js/src/jsdate.cpp
author ffxbld <ffxbld@mozilla.com>
Thu, 05 Dec 2019 10:08:34 +0000
changeset 563505 7067896c7696e3f5cf3b76ff53ecad8d65e9cc30
parent 561043 f49089ef86eaa3bddd19ecd05a7c9d361fadc67f
permissions -rw-r--r--
No Bug, mozilla-release repo-update blocklist remote-settings - a=repo-update r=RyanVM Differential Revision: https://phabricator.services.mozilla.com/D55932

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
 * JS date methods.
 *
 * "For example, OS/360 devotes 26 bytes of the permanently
 *  resident date-turnover routine to the proper handling of
 *  December 31 on leap years (when it is Day 366).  That
 *  might have been left to the operator."
 *
 * Frederick Brooks, 'The Second-System Effect'.
 */

#include "jsdate.h"

#include "mozilla/ArrayUtils.h"
#include "mozilla/Atomics.h"
#include "mozilla/Casting.h"
#include "mozilla/FloatingPoint.h"
#include "mozilla/Sprintf.h"
#include "mozilla/TextUtils.h"

#include <math.h>
#include <string.h>

#include "jsapi.h"
#include "jsfriendapi.h"
#include "jsnum.h"
#include "jstypes.h"
#include "jsutil.h"

#include "js/Conversions.h"
#include "js/Date.h"
#include "js/LocaleSensitive.h"
#include "js/PropertySpec.h"
#include "js/Wrapper.h"
#include "util/StringBuffer.h"
#include "util/Text.h"
#include "vm/DateObject.h"
#include "vm/DateTime.h"
#include "vm/GlobalObject.h"
#include "vm/Interpreter.h"
#include "vm/JSContext.h"
#include "vm/JSObject.h"
#include "vm/StringType.h"
#include "vm/Time.h"

#include "vm/JSObject-inl.h"

using namespace js;

using mozilla::ArrayLength;
using mozilla::Atomic;
using mozilla::BitwiseCast;
using mozilla::IsAsciiAlpha;
using mozilla::IsAsciiDigit;
using mozilla::IsFinite;
using mozilla::IsNaN;
using mozilla::NumbersAreIdentical;
using mozilla::Relaxed;

using JS::AutoCheckCannotGC;
using JS::ClippedTime;
using JS::GenericNaN;
using JS::TimeClip;
using JS::ToInteger;

// When this value is non-zero, we'll round the time by this resolution.
static Atomic<uint32_t, Relaxed> sResolutionUsec;
// This is not implemented yet, but we will use this to know to jitter the time
// in the JS shell
static Atomic<bool, Relaxed> sJitter;
// The callback we will use for the Gecko implementation of Timer
// Clamping/Jittering
static Atomic<JS::ReduceMicrosecondTimePrecisionCallback, Relaxed>
    sReduceMicrosecondTimePrecisionCallback;

/*
 * The JS 'Date' object is patterned after the Java 'Date' object.
 * Here is a script:
 *
 *    today = new Date();
 *
 *    print(today.toLocaleString());
 *
 *    weekDay = today.getDay();
 *
 *
 * These Java (and ECMA-262) methods are supported:
 *
 *     UTC
 *     getDate (getUTCDate)
 *     getDay (getUTCDay)
 *     getHours (getUTCHours)
 *     getMinutes (getUTCMinutes)
 *     getMonth (getUTCMonth)
 *     getSeconds (getUTCSeconds)
 *     getMilliseconds (getUTCMilliseconds)
 *     getTime
 *     getTimezoneOffset
 *     getYear
 *     getFullYear (getUTCFullYear)
 *     parse
 *     setDate (setUTCDate)
 *     setHours (setUTCHours)
 *     setMinutes (setUTCMinutes)
 *     setMonth (setUTCMonth)
 *     setSeconds (setUTCSeconds)
 *     setMilliseconds (setUTCMilliseconds)
 *     setTime
 *     setYear (setFullYear, setUTCFullYear)
 *     toGMTString (toUTCString)
 *     toLocaleString
 *     toString
 *
 *
 * These Java methods are not supported
 *
 *     setDay
 *     before
 *     after
 *     equals
 *     hashCode
 */

namespace {

class DateTimeHelper {
 private:
#if ENABLE_INTL_API && !MOZ_SYSTEM_ICU
  static double localTZA(double t, DateTimeInfo::TimeZoneOffset offset);
#else
  static int equivalentYearForDST(int year);
  static bool isRepresentableAsTime32(double t);
  static double daylightSavingTA(double t);
  static double adjustTime(double date);
  static PRMJTime toPRMJTime(double localTime, double utcTime);
#endif

 public:
  static double localTime(double t);
  static double UTC(double t);
  static JSString* timeZoneComment(JSContext* cx, double utcTime,
                                   double localTime);
#if !ENABLE_INTL_API || MOZ_SYSTEM_ICU
  static size_t formatTime(char* buf, size_t buflen, const char* fmt,
                           double utcTime, double localTime);
#endif
};

}  // namespace

// ES2019 draft rev 0ceb728a1adbffe42b26972a6541fd7f398b1557
// 5.2.5 Mathematical Operations
static inline double PositiveModulo(double dividend, double divisor) {
  MOZ_ASSERT(divisor > 0);
  MOZ_ASSERT(IsFinite(divisor));

  double result = fmod(dividend, divisor);
  if (result < 0) {
    result += divisor;
  }
  return result + (+0.0);
}

static inline double Day(double t) { return floor(t / msPerDay); }

static double TimeWithinDay(double t) { return PositiveModulo(t, msPerDay); }

/* ES5 15.9.1.3. */
static inline bool IsLeapYear(double year) {
  MOZ_ASSERT(ToInteger(year) == year);
  return fmod(year, 4) == 0 && (fmod(year, 100) != 0 || fmod(year, 400) == 0);
}

static inline double DaysInYear(double year) {
  if (!IsFinite(year)) {
    return GenericNaN();
  }
  return IsLeapYear(year) ? 366 : 365;
}

static inline double DayFromYear(double y) {
  return 365 * (y - 1970) + floor((y - 1969) / 4.0) -
         floor((y - 1901) / 100.0) + floor((y - 1601) / 400.0);
}

static inline double TimeFromYear(double y) {
  return DayFromYear(y) * msPerDay;
}

static double YearFromTime(double t) {
  if (!IsFinite(t)) {
    return GenericNaN();
  }

  MOZ_ASSERT(ToInteger(t) == t);

  double y = floor(t / (msPerDay * 365.2425)) + 1970;
  double t2 = TimeFromYear(y);

  /*
   * Adjust the year if the approximation was wrong.  Since the year was
   * computed using the average number of ms per year, it will usually
   * be wrong for dates within several hours of a year transition.
   */
  if (t2 > t) {
    y--;
  } else {
    if (t2 + msPerDay * DaysInYear(y) <= t) {
      y++;
    }
  }
  return y;
}

static inline int DaysInFebruary(double year) {
  return IsLeapYear(year) ? 29 : 28;
}

/* ES5 15.9.1.4. */
static inline double DayWithinYear(double t, double year) {
  MOZ_ASSERT_IF(IsFinite(t), YearFromTime(t) == year);
  return Day(t) - DayFromYear(year);
}

static double MonthFromTime(double t) {
  if (!IsFinite(t)) {
    return GenericNaN();
  }

  double year = YearFromTime(t);
  double d = DayWithinYear(t, year);

  int step;
  if (d < (step = 31)) {
    return 0;
  }
  if (d < (step += DaysInFebruary(year))) {
    return 1;
  }
  if (d < (step += 31)) {
    return 2;
  }
  if (d < (step += 30)) {
    return 3;
  }
  if (d < (step += 31)) {
    return 4;
  }
  if (d < (step += 30)) {
    return 5;
  }
  if (d < (step += 31)) {
    return 6;
  }
  if (d < (step += 31)) {
    return 7;
  }
  if (d < (step += 30)) {
    return 8;
  }
  if (d < (step += 31)) {
    return 9;
  }
  if (d < (step += 30)) {
    return 10;
  }
  return 11;
}

/* ES5 15.9.1.5. */
static double DateFromTime(double t) {
  if (!IsFinite(t)) {
    return GenericNaN();
  }

  double year = YearFromTime(t);
  double d = DayWithinYear(t, year);

  int next;
  if (d <= (next = 30)) {
    return d + 1;
  }
  int step = next;
  if (d <= (next += DaysInFebruary(year))) {
    return d - step;
  }
  step = next;
  if (d <= (next += 31)) {
    return d - step;
  }
  step = next;
  if (d <= (next += 30)) {
    return d - step;
  }
  step = next;
  if (d <= (next += 31)) {
    return d - step;
  }
  step = next;
  if (d <= (next += 30)) {
    return d - step;
  }
  step = next;
  if (d <= (next += 31)) {
    return d - step;
  }
  step = next;
  if (d <= (next += 31)) {
    return d - step;
  }
  step = next;
  if (d <= (next += 30)) {
    return d - step;
  }
  step = next;
  if (d <= (next += 31)) {
    return d - step;
  }
  step = next;
  if (d <= (next += 30)) {
    return d - step;
  }
  step = next;
  return d - step;
}

/* ES5 15.9.1.6. */
static int WeekDay(double t) {
  /*
   * We can't assert TimeClip(t) == t because we call this function with
   * local times, which can be offset outside TimeClip's permitted range.
   */
  MOZ_ASSERT(ToInteger(t) == t);
  int result = (int(Day(t)) + 4) % 7;
  if (result < 0) {
    result += 7;
  }
  return result;
}

static inline int DayFromMonth(int month, bool isLeapYear) {
  /*
   * The following array contains the day of year for the first day of
   * each month, where index 0 is January, and day 0 is January 1.
   */
  static const int firstDayOfMonth[2][13] = {
      {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},
      {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}};

  MOZ_ASSERT(0 <= month && month <= 12);
  return firstDayOfMonth[isLeapYear][month];
}

template <typename T>
static inline int DayFromMonth(T month, bool isLeapYear) = delete;

/* ES5 15.9.1.12 (out of order to accommodate DaylightSavingTA). */
static double MakeDay(double year, double month, double date) {
  /* Step 1. */
  if (!IsFinite(year) || !IsFinite(month) || !IsFinite(date)) {
    return GenericNaN();
  }

  /* Steps 2-4. */
  double y = ToInteger(year);
  double m = ToInteger(month);
  double dt = ToInteger(date);

  /* Step 5. */
  double ym = y + floor(m / 12);

  /* Step 6. */
  int mn = int(PositiveModulo(m, 12));

  /* Steps 7-8. */
  bool leap = IsLeapYear(ym);

  double yearday = floor(TimeFromYear(ym) / msPerDay);
  double monthday = DayFromMonth(mn, leap);

  return yearday + monthday + dt - 1;
}

/* ES5 15.9.1.13 (out of order to accommodate DaylightSavingTA). */
static inline double MakeDate(double day, double time) {
  /* Step 1. */
  if (!IsFinite(day) || !IsFinite(time)) {
    return GenericNaN();
  }

  /* Step 2. */
  return day * msPerDay + time;
}

JS_PUBLIC_API double JS::MakeDate(double year, unsigned month, unsigned day) {
  MOZ_ASSERT(month <= 11);
  MOZ_ASSERT(day >= 1 && day <= 31);

  return ::MakeDate(MakeDay(year, month, day), 0);
}

JS_PUBLIC_API double JS::MakeDate(double year, unsigned month, unsigned day,
                                  double time) {
  MOZ_ASSERT(month <= 11);
  MOZ_ASSERT(day >= 1 && day <= 31);

  return ::MakeDate(MakeDay(year, month, day), time);
}

JS_PUBLIC_API double JS::YearFromTime(double time) {
  return ::YearFromTime(time);
}

JS_PUBLIC_API double JS::MonthFromTime(double time) {
  return ::MonthFromTime(time);
}

JS_PUBLIC_API double JS::DayFromTime(double time) { return DateFromTime(time); }

JS_PUBLIC_API double JS::DayFromYear(double year) {
  return ::DayFromYear(year);
}

JS_PUBLIC_API double JS::DayWithinYear(double time, double year) {
  return ::DayWithinYear(time, year);
}

JS_PUBLIC_API void JS::SetReduceMicrosecondTimePrecisionCallback(
    JS::ReduceMicrosecondTimePrecisionCallback callback) {
  sReduceMicrosecondTimePrecisionCallback = callback;
}

JS_PUBLIC_API void JS::SetTimeResolutionUsec(uint32_t resolution, bool jitter) {
  sResolutionUsec = resolution;
  sJitter = jitter;
}

#if ENABLE_INTL_API && !MOZ_SYSTEM_ICU
// ES2019 draft rev 0ceb728a1adbffe42b26972a6541fd7f398b1557
// 20.3.1.7 LocalTZA ( t, isUTC )
double DateTimeHelper::localTZA(double t, DateTimeInfo::TimeZoneOffset offset) {
  MOZ_ASSERT(IsFinite(t));

  int64_t milliseconds = static_cast<int64_t>(t);
  int32_t offsetMilliseconds =
      DateTimeInfo::getOffsetMilliseconds(milliseconds, offset);
  return static_cast<double>(offsetMilliseconds);
}

// ES2019 draft rev 0ceb728a1adbffe42b26972a6541fd7f398b1557
// 20.3.1.8 LocalTime ( t )
double DateTimeHelper::localTime(double t) {
  if (!IsFinite(t)) {
    return GenericNaN();
  }

  MOZ_ASSERT(StartOfTime <= t && t <= EndOfTime);
  return t + localTZA(t, DateTimeInfo::TimeZoneOffset::UTC);
}

// ES2019 draft rev 0ceb728a1adbffe42b26972a6541fd7f398b1557
// 20.3.1.9 UTC ( t )
double DateTimeHelper::UTC(double t) {
  if (!IsFinite(t)) {
    return GenericNaN();
  }

  if (t < (StartOfTime - msPerDay) || t > (EndOfTime + msPerDay)) {
    return GenericNaN();
  }

  return t - localTZA(t, DateTimeInfo::TimeZoneOffset::Local);
}
#else
/*
 * Find a year for which any given date will fall on the same weekday.
 *
 * This function should be used with caution when used other than
 * for determining DST; it hasn't been proven not to produce an
 * incorrect year for times near year boundaries.
 */
int DateTimeHelper::equivalentYearForDST(int year) {
  /*
   * Years and leap years on which Jan 1 is a Sunday, Monday, etc.
   *
   * yearStartingWith[0][i] is an example non-leap year where
   * Jan 1 appears on Sunday (i == 0), Monday (i == 1), etc.
   *
   * yearStartingWith[1][i] is an example leap year where
   * Jan 1 appears on Sunday (i == 0), Monday (i == 1), etc.
   *
   * Keep two different mappings, one for past years (< 1970), and a
   * different one for future years (> 2037).
   */
  static const int pastYearStartingWith[2][7] = {
      {1978, 1973, 1974, 1975, 1981, 1971, 1977},
      {1984, 1996, 1980, 1992, 1976, 1988, 1972}};
  static const int futureYearStartingWith[2][7] = {
      {2034, 2035, 2030, 2031, 2037, 2027, 2033},
      {2012, 2024, 2036, 2020, 2032, 2016, 2028}};

  int day = int(DayFromYear(year) + 4) % 7;
  if (day < 0) {
    day += 7;
  }

  const auto& yearStartingWith =
      year < 1970 ? pastYearStartingWith : futureYearStartingWith;
  return yearStartingWith[IsLeapYear(year)][day];
}

// Return true if |t| is representable as a 32-bit time_t variable, that means
// the year is in [1970, 2038).
bool DateTimeHelper::isRepresentableAsTime32(double t) {
  return 0.0 <= t && t < 2145916800000.0;
}

/* ES5 15.9.1.8. */
double DateTimeHelper::daylightSavingTA(double t) {
  if (!IsFinite(t)) {
    return GenericNaN();
  }

  /*
   * If earlier than 1970 or after 2038, potentially beyond the ken of
   * many OSes, map it to an equivalent year before asking.
   */
  if (!isRepresentableAsTime32(t)) {
    int year = equivalentYearForDST(int(YearFromTime(t)));
    double day = MakeDay(year, MonthFromTime(t), DateFromTime(t));
    t = MakeDate(day, TimeWithinDay(t));
  }

  int64_t utcMilliseconds = static_cast<int64_t>(t);
  int32_t offsetMilliseconds =
      DateTimeInfo::getDSTOffsetMilliseconds(utcMilliseconds);
  return static_cast<double>(offsetMilliseconds);
}

double DateTimeHelper::adjustTime(double date) {
  double localTZA = DateTimeInfo::localTZA();
  double t = daylightSavingTA(date) + localTZA;
  t = (localTZA >= 0) ? fmod(t, msPerDay) : -fmod(msPerDay - t, msPerDay);
  return t;
}

/* ES5 15.9.1.9. */
double DateTimeHelper::localTime(double t) { return t + adjustTime(t); }

double DateTimeHelper::UTC(double t) {
  // Following the ES2017 specification creates undesirable results at DST
  // transitions. For example when transitioning from PST to PDT,
  // |new Date(2016,2,13,2,0,0).toTimeString()| returns the string value
  // "01:00:00 GMT-0800 (PST)" instead of "03:00:00 GMT-0700 (PDT)". Follow
  // V8 and subtract one hour before computing the offset.
  // Spec bug: https://bugs.ecmascript.org/show_bug.cgi?id=4007

  return t - adjustTime(t - DateTimeInfo::localTZA() - msPerHour);
}
#endif /* ENABLE_INTL_API && !MOZ_SYSTEM_ICU */

static double LocalTime(double t) { return DateTimeHelper::localTime(t); }

static double UTC(double t) { return DateTimeHelper::UTC(t); }

/* ES5 15.9.1.10. */
static double HourFromTime(double t) {
  return PositiveModulo(floor(t / msPerHour), HoursPerDay);
}

static double MinFromTime(double t) {
  return PositiveModulo(floor(t / msPerMinute), MinutesPerHour);
}

static double SecFromTime(double t) {
  return PositiveModulo(floor(t / msPerSecond), SecondsPerMinute);
}

static double msFromTime(double t) { return PositiveModulo(t, msPerSecond); }

/* ES5 15.9.1.11. */
static double MakeTime(double hour, double min, double sec, double ms) {
  /* Step 1. */
  if (!IsFinite(hour) || !IsFinite(min) || !IsFinite(sec) || !IsFinite(ms)) {
    return GenericNaN();
  }

  /* Step 2. */
  double h = ToInteger(hour);

  /* Step 3. */
  double m = ToInteger(min);

  /* Step 4. */
  double s = ToInteger(sec);

  /* Step 5. */
  double milli = ToInteger(ms);

  /* Steps 6-7. */
  return h * msPerHour + m * msPerMinute + s * msPerSecond + milli;
}

/**
 * end of ECMA 'support' functions
 */

/* for use by date_parse */

static const char* const wtb[] = {
    // clang-format off
    "am", "pm",
    "monday", "tuesday", "wednesday", "thursday", "friday",
    "saturday", "sunday",
    "january", "february", "march", "april", "may", "june",
    "july", "august", "september", "october", "november", "december",
    "gmt", "ut", "utc",
    "est", "edt",
    "cst", "cdt",
    "mst", "mdt",
    "pst", "pdt"
    /* time zone table needs to be expanded */
    // clang-format on
};

static const int ttb[] = {
    // clang-format off
    -1, -2, 0, 0, 0, 0, 0, 0, 0,       /* AM/PM */
    2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
    10000 + 0, 10000 + 0, 10000 + 0,   /* GMT/UT/UTC */
    10000 + 5 * 60, 10000 + 4 * 60,    /* EST/EDT */
    10000 + 6 * 60, 10000 + 5 * 60,    /* CST/CDT */
    10000 + 7 * 60, 10000 + 6 * 60,    /* MST/MDT */
    10000 + 8 * 60, 10000 + 7 * 60     /* PST/PDT */
    // clang-format on
};

template <typename CharT>
static bool RegionMatches(const char* s1, int s1off, const CharT* s2, int s2off,
                          int count) {
  while (count > 0 && s1[s1off] && s2[s2off]) {
    if (unicode::ToLowerCase(s1[s1off]) != unicode::ToLowerCase(s2[s2off])) {
      break;
    }

    s1off++;
    s2off++;
    count--;
  }

  return count == 0;
}

// ES2017 draft rev (TODO: Add git hash when PR 642 is merged.)
// 20.3.3.4
// Date.UTC(year [, month [, date [, hours [, minutes [, seconds [, ms]]]]]])
static bool date_UTC(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  // Step 1.
  double y;
  if (!ToNumber(cx, args.get(0), &y)) {
    return false;
  }

  // Step 2.
  double m;
  if (args.length() >= 2) {
    if (!ToNumber(cx, args[1], &m)) {
      return false;
    }
  } else {
    m = 0;
  }

  // Step 3.
  double dt;
  if (args.length() >= 3) {
    if (!ToNumber(cx, args[2], &dt)) {
      return false;
    }
  } else {
    dt = 1;
  }

  // Step 4.
  double h;
  if (args.length() >= 4) {
    if (!ToNumber(cx, args[3], &h)) {
      return false;
    }
  } else {
    h = 0;
  }

  // Step 5.
  double min;
  if (args.length() >= 5) {
    if (!ToNumber(cx, args[4], &min)) {
      return false;
    }
  } else {
    min = 0;
  }

  // Step 6.
  double s;
  if (args.length() >= 6) {
    if (!ToNumber(cx, args[5], &s)) {
      return false;
    }
  } else {
    s = 0;
  }

  // Step 7.
  double milli;
  if (args.length() >= 7) {
    if (!ToNumber(cx, args[6], &milli)) {
      return false;
    }
  } else {
    milli = 0;
  }

  // Step 8.
  double yr = y;
  if (!IsNaN(y)) {
    double yint = ToInteger(y);
    if (0 <= yint && yint <= 99) {
      yr = 1900 + yint;
    }
  }

  // Step 9.
  ClippedTime time =
      TimeClip(MakeDate(MakeDay(yr, m, dt), MakeTime(h, min, s, milli)));
  args.rval().set(TimeValue(time));
  return true;
}

/*
 * Read and convert decimal digits from s[*i] into *result
 * while *i < limit.
 *
 * Succeed if any digits are converted. Advance *i only
 * as digits are consumed.
 */
template <typename CharT>
static bool ParseDigits(size_t* result, const CharT* s, size_t* i,
                        size_t limit) {
  size_t init = *i;
  *result = 0;
  while (*i < limit && ('0' <= s[*i] && s[*i] <= '9')) {
    *result *= 10;
    *result += (s[*i] - '0');
    ++(*i);
  }
  return *i != init;
}

/*
 * Read and convert decimal digits to the right of a decimal point,
 * representing a fractional integer, from s[*i] into *result
 * while *i < limit.
 *
 * Succeed if any digits are converted. Advance *i only
 * as digits are consumed.
 */
template <typename CharT>
static bool ParseFractional(double* result, const CharT* s, size_t* i,
                            size_t limit) {
  double factor = 0.1;
  size_t init = *i;
  *result = 0.0;
  while (*i < limit && ('0' <= s[*i] && s[*i] <= '9')) {
    *result += (s[*i] - '0') * factor;
    factor *= 0.1;
    ++(*i);
  }
  return *i != init;
}

/*
 * Read and convert exactly n decimal digits from s[*i]
 * to s[min(*i+n,limit)] into *result.
 *
 * Succeed if exactly n digits are converted. Advance *i only
 * on success.
 */
template <typename CharT>
static bool ParseDigitsN(size_t n, size_t* result, const CharT* s, size_t* i,
                         size_t limit) {
  size_t init = *i;

  if (ParseDigits(result, s, i, Min(limit, init + n))) {
    return (*i - init) == n;
  }

  *i = init;
  return false;
}

/*
 * Read and convert n or less decimal digits from s[*i]
 * to s[min(*i+n,limit)] into *result.
 *
 * Succeed only if greater than zero but less than or equal to n digits are
 * converted. Advance *i only on success.
 */
template <typename CharT>
static bool ParseDigitsNOrLess(size_t n, size_t* result, const CharT* s,
                               size_t* i, size_t limit) {
  size_t init = *i;

  if (ParseDigits(result, s, i, Min(limit, init + n))) {
    return ((*i - init) > 0) && ((*i - init) <= n);
  }

  *i = init;
  return false;
}

static int DaysInMonth(int year, int month) {
  bool leap = IsLeapYear(year);
  int result = int(DayFromMonth(month, leap) - DayFromMonth(month - 1, leap));
  return result;
}

/*
 * Parse a string according to the formats specified in section 20.3.1.16
 * of the ECMAScript standard. These formats are based upon a simplification
 * of the ISO 8601 Extended Format. As per the spec omitted month and day
 * values are defaulted to '01', omitted HH:mm:ss values are defaulted to '00'
 * and an omitted sss field is defaulted to '000'.
 *
 * For cross compatibility we allow the following extensions.
 *
 * These are:
 *
 *   Standalone time part:
 *     Any of the time formats below can be parsed without a date part.
 *     E.g. "T19:00:00Z" will parse successfully. The date part will then
 *     default to 1970-01-01.
 *
 *   'T' from the time part may be replaced with a space character:
 *     "1970-01-01 12:00:00Z" will parse successfully. Note that only a single
 *     space is permitted and this is not permitted in the standalone
 *     version above.
 *
 *   One or more decimal digits for milliseconds:
 *     The specification requires exactly three decimal digits for
 *     the fractional part but we allow for one or more digits.
 *
 *   Time zone specifier without ':':
 *     We allow the time zone to be specified without a ':' character.
 *     E.g. "T19:00:00+0700" is equivalent to "T19:00:00+07:00".
 *
 *   One or two digits for months, days, hours, minutes and seconds:
 *     The specification requires exactly two decimal digits for the fields
 *     above. We allow for one or two decimal digits. I.e. "1970-1-1" is
 *     equivalent to "1970-01-01".
 *
 * Date part:
 *
 *  Year:
 *     YYYY (eg 1997)
 *
 *  Year and month:
 *     YYYY-MM (eg 1997-07)
 *
 *  Complete date:
 *     YYYY-MM-DD (eg 1997-07-16)
 *
 * Time part:
 *
 *  Hours and minutes:
 *     Thh:mmTZD (eg T19:20+01:00)
 *
 *  Hours, minutes and seconds:
 *     Thh:mm:ssTZD (eg T19:20:30+01:00)
 *
 *  Hours, minutes, seconds and a decimal fraction of a second:
 *     Thh:mm:ss.sTZD (eg T19:20:30.45+01:00)
 *
 * where:
 *
 *   YYYY = four-digit year or six digit year as +YYYYYY or -YYYYYY
 *   MM   = one or two-digit month (01=January, etc.)
 *   DD   = one or two-digit day of month (01 through 31)
 *   hh   = one or two digits of hour (00 through 23) (am/pm NOT allowed)
 *   mm   = one or two digits of minute (00 through 59)
 *   ss   = one or two digits of second (00 through 59)
 *   sss  = one or more digits representing a decimal fraction of a second
 *   TZD  = time zone designator (Z or +hh:mm or -hh:mm or missing for local)
 */
template <typename CharT>
static bool ParseISOStyleDate(const CharT* s, size_t length,
                              ClippedTime* result) {
  size_t i = 0;
  size_t pre = 0;
  int tzMul = 1;
  int dateMul = 1;
  size_t year = 1970;
  size_t month = 1;
  size_t day = 1;
  size_t hour = 0;
  size_t min = 0;
  size_t sec = 0;
  double frac = 0;
  bool isLocalTime = false;
  size_t tzHour = 0;
  size_t tzMin = 0;
  bool isPermissive = false;
  bool isStrict = false;

#define PEEK(ch) (i < length && s[i] == ch)

#define NEED(ch)                   \
  if (i >= length || s[i] != ch) { \
    return false;                  \
  } else {                         \
    ++i;                           \
  }

#define DONE_DATE_UNLESS(ch)       \
  if (i >= length || s[i] != ch) { \
    goto done_date;                \
  } else {                         \
    ++i;                           \
  }

#define DONE_UNLESS(ch)            \
  if (i >= length || s[i] != ch) { \
    goto done;                     \
  } else {                         \
    ++i;                           \
  }

#define NEED_NDIGITS(n, field)                   \
  if (!ParseDigitsN(n, &field, s, &i, length)) { \
    return false;                                \
  }

#define NEED_NDIGITS_OR_LESS(n, field)                 \
  pre = i;                                             \
  if (!ParseDigitsNOrLess(n, &field, s, &i, length)) { \
    return false;                                      \
  }                                                    \
  if (i < pre + (n)) {                                 \
    if (isStrict) {                                    \
      return false;                                    \
    } else {                                           \
      isPermissive = true;                             \
    }                                                  \
  }

  if (PEEK('+') || PEEK('-')) {
    if (PEEK('-')) {
      dateMul = -1;
    }
    ++i;
    NEED_NDIGITS(6, year);
  } else {
    NEED_NDIGITS(4, year);
  }
  DONE_DATE_UNLESS('-');
  NEED_NDIGITS_OR_LESS(2, month);
  DONE_DATE_UNLESS('-');
  NEED_NDIGITS_OR_LESS(2, day);

done_date:
  if (PEEK('T')) {
    if (isPermissive) {
      // Require standard format "[+00]1970-01-01" if a time part marker "T"
      // exists
      return false;
    }
    isStrict = true;
    i++;
  } else if (PEEK(' ')) {
    i++;
  } else {
    goto done;
  }

  NEED_NDIGITS_OR_LESS(2, hour);
  NEED(':');
  NEED_NDIGITS_OR_LESS(2, min);

  if (PEEK(':')) {
    ++i;
    NEED_NDIGITS_OR_LESS(2, sec);
    if (PEEK('.')) {
      ++i;
      if (!ParseFractional(&frac, s, &i, length)) {
        return false;
      }
    }
  }

  if (PEEK('Z')) {
    ++i;
  } else if (PEEK('+') || PEEK('-')) {
    if (PEEK('-')) {
      tzMul = -1;
    }
    ++i;
    NEED_NDIGITS(2, tzHour);
    /*
     * Non-standard extension to the ISO date format (permitted by ES5):
     * allow "-0700" as a time zone offset, not just "-07:00".
     */
    if (PEEK(':')) {
      ++i;
    }
    NEED_NDIGITS(2, tzMin);
  } else {
    isLocalTime = true;
  }

done:
  if (year > 275943  // ceil(1e8/365) + 1970
      || (month == 0 || month > 12) ||
      (day == 0 || day > size_t(DaysInMonth(year, month))) || hour > 24 ||
      ((hour == 24) && (min > 0 || sec > 0 || frac > 0)) || min > 59 ||
      sec > 59 || tzHour > 23 || tzMin > 59) {
    return false;
  }

  if (i != length) {
    return false;
  }

  month -= 1; /* convert month to 0-based */

  double msec = MakeDate(MakeDay(dateMul * double(year), month, day),
                         MakeTime(hour, min, sec, frac * 1000.0));

  if (isLocalTime) {
    msec = UTC(msec);
  } else {
    msec -= tzMul * (tzHour * msPerHour + tzMin * msPerMinute);
  }

  *result = TimeClip(msec);
  return NumbersAreIdentical(msec, result->toDouble());

#undef PEEK
#undef NEED
#undef DONE_UNLESS
#undef NEED_NDIGITS
#undef NEED_NDIGITS_OR_LESS
}

template <typename CharT>
static bool ParseDate(const CharT* s, size_t length, ClippedTime* result) {
  if (ParseISOStyleDate(s, length, result)) {
    return true;
  }

  if (length == 0) {
    return false;
  }

  int year = -1;
  int mon = -1;
  int mday = -1;
  int hour = -1;
  int min = -1;
  int sec = -1;
  int tzOffset = -1;

  // One of '+', '-', ':', '/', or 0 (the default value).
  int prevc = 0;

  bool seenPlusMinus = false;
  bool seenMonthName = false;
  bool seenFullYear = false;
  bool negativeYear = false;

  size_t i = 0;
  while (i < length) {
    int c = s[i];
    i++;
    if (c <= ' ' || c == ',' || c == '-') {
      if (c == '-' && '0' <= s[i] && s[i] <= '9') {
        prevc = c;
      }
      continue;
    }
    if (c == '(') { /* comments) */
      int depth = 1;
      while (i < length) {
        c = s[i];
        i++;
        if (c == '(') {
          depth++;
        } else if (c == ')') {
          if (--depth <= 0) {
            break;
          }
        }
      }
      continue;
    }
    if ('0' <= c && c <= '9') {
      size_t partStart = i - 1;
      uint32_t u = c - '0';
      while (i < length && '0' <= (c = s[i]) && c <= '9') {
        u = u * 10 + (c - '0');
        i++;
      }
      size_t partLength = i - partStart;

      int n = int(u);

      /*
       * Allow TZA before the year, so 'Wed Nov 05 21:49:11 GMT-0800 1997'
       * works.
       *
       * Uses of seenPlusMinus allow ':' in TZA, so Java no-timezone style
       * of GMT+4:30 works.
       */

      if (prevc == '-' && (tzOffset != 0 || seenPlusMinus) && partLength >= 4 &&
          year < 0) {
        // Parse as a negative, possibly zero-padded year if
        // 1. the preceding character is '-',
        // 2. the TZA is not 'GMT' (tested by |tzOffset != 0|),
        // 3. or a TZA was already parsed |seenPlusMinus == true|,
        // 4. the part length is at least 4 (to parse '-08' as a TZA),
        // 5. and we did not already parse a year |year < 0|.
        year = n;
        seenFullYear = true;
        negativeYear = true;
      } else if ((prevc == '+' || prevc == '-') /*  && year>=0 */) {
        /* Make ':' case below change tzOffset. */
        seenPlusMinus = true;

        /* offset */
        if (n < 24) {
          n = n * 60; /* EG. "GMT-3" */
        } else {
          n = n % 100 + n / 100 * 60; /* eg "GMT-0430" */
        }

        if (prevc == '+') /* plus means east of GMT */
          n = -n;

        // Reject if not preceded by 'GMT' or if a time zone offset
        // was already parsed.
        if (tzOffset != 0 && tzOffset != -1) {
          return false;
        }

        tzOffset = n;
      } else if (prevc == '/' && mon >= 0 && mday >= 0 && year < 0) {
        if (c <= ' ' || c == ',' || c == '/' || i >= length) {
          year = n;
        } else {
          return false;
        }
      } else if (c == ':') {
        if (hour < 0) {
          hour = /*byte*/ n;
        } else if (min < 0) {
          min = /*byte*/ n;
        } else {
          return false;
        }
      } else if (c == '/') {
        /*
         * Until it is determined that mon is the actual month, keep
         * it as 1-based rather than 0-based.
         */
        if (mon < 0) {
          mon = /*byte*/ n;
        } else if (mday < 0) {
          mday = /*byte*/ n;
        } else {
          return false;
        }
      } else if (i < length && c != ',' && c > ' ' && c != '-' && c != '(') {
        return false;
      } else if (seenPlusMinus && n < 60) { /* handle GMT-3:30 */
        if (tzOffset < 0) {
          tzOffset -= n;
        } else {
          tzOffset += n;
        }
      } else if (hour >= 0 && min < 0) {
        min = /*byte*/ n;
      } else if (prevc == ':' && min >= 0 && sec < 0) {
        sec = /*byte*/ n;
      } else if (mon < 0) {
        mon = /*byte*/ n;
      } else if (mon >= 0 && mday < 0) {
        mday = /*byte*/ n;
      } else if (mon >= 0 && mday >= 0 && year < 0) {
        year = n;
        seenFullYear = partLength >= 4;
      } else {
        return false;
      }
      prevc = 0;
    } else if (c == '/' || c == ':' || c == '+' || c == '-') {
      prevc = c;
    } else {
      size_t st = i - 1;
      while (i < length) {
        c = s[i];
        if (!IsAsciiAlpha(c)) {
          break;
        }
        i++;
      }

      if (i <= st + 1) {
        return false;
      }

      int k;
      for (k = ArrayLength(wtb); --k >= 0;) {
        if (RegionMatches(wtb[k], 0, s, st, i - st)) {
          int action = ttb[k];
          if (action != 0) {
            if (action < 0) {
              /*
               * AM/PM. Count 12:30 AM as 00:30, 12:30 PM as
               * 12:30, instead of blindly adding 12 if PM.
               */
              MOZ_ASSERT(action == -1 || action == -2);
              if (hour > 12 || hour < 0) {
                return false;
              }

              if (action == -1 && hour == 12) /* am */
                hour = 0;
              else if (action == -2 && hour != 12) /* pm */
                hour += 12;
            } else if (action <= 13) { /* month! */
              /*
               * Adjust mon to be 1-based until the final values
               * for mon, mday and year are adjusted below.
               */
              if (seenMonthName) {
                return false;
              }

              seenMonthName = true;
              int temp = /*byte*/ (action - 2) + 1;

              if (mon < 0) {
                mon = temp;
              } else if (mday < 0) {
                mday = mon;
                mon = temp;
              } else if (year < 0) {
                year = mon;
                mon = temp;
              } else {
                return false;
              }
            } else {
              tzOffset = action - 10000;
            }
          }
          break;
        }
      }

      if (k < 0) {
        return false;
      }

      prevc = 0;
    }
  }

  if (year < 0 || mon < 0 || mday < 0) {
    return false;
  }

  /*
   * Case 1. The input string contains an English month name.
   *         The form of the string can be month f l, or f month l, or
   *         f l month which each evaluate to the same date.
   *         If f and l are both greater than or equal to 100 the date
   *         is invalid.
   *
   *         The year is taken to be either the greater of the values f, l or
   *         whichever is set to zero.
   *
   * Case 2. The input string is of the form "f/m/l" where f, m and l are
   *         integers, e.g. 7/16/45. mon, mday and year values are adjusted
   *         to achieve Chrome compatibility.
   *
   *         a. If 0 < f <= 12 and 0 < l <= 31, f/m/l is interpreted as
   *         month/day/year.
   *         b. If 31 < f and 0 < m <= 12 and 0 < l <= 31 f/m/l is
   *         interpreted as year/month/day
   */
  if (seenMonthName) {
    if (mday >= 100 && mon >= 100) {
      return false;
    }

    if (year > 0 && (mday == 0 || mday > year) && !seenFullYear) {
      int temp = year;
      year = mday;
      mday = temp;
    }

    if (mday <= 0 || mday > 31) {
      return false;
    }

  } else if (0 < mon && mon <= 12 && 0 < mday && mday <= 31) {
    /* (a) month/day/year */
  } else {
    /* (b) year/month/day */
    if (mon > 31 && mday <= 12 && year <= 31 && !seenFullYear) {
      int temp = year;
      year = mon;
      mon = mday;
      mday = temp;
    } else {
      return false;
    }
  }

  // If the year is greater than or equal to 50 and less than 100, it is
  // considered to be the number of years after 1900. If the year is less
  // than 50 it is considered to be the number of years after 2000,
  // otherwise it is considered to be the number of years after 0.
  if (!seenFullYear) {
    if (year < 50) {
      year += 2000;
    } else if (year >= 50 && year < 100) {
      year += 1900;
    }
  }

  if (negativeYear) {
    year = -year;
  }

  mon -= 1; /* convert month to 0-based */
  if (sec < 0) {
    sec = 0;
  }
  if (min < 0) {
    min = 0;
  }
  if (hour < 0) {
    hour = 0;
  }

  double msec = MakeDate(MakeDay(year, mon, mday), MakeTime(hour, min, sec, 0));

  if (tzOffset == -1) { /* no time zone specified, have to use local */
    msec = UTC(msec);
  } else {
    msec += tzOffset * msPerMinute;
  }

  *result = TimeClip(msec);
  return true;
}

static bool ParseDate(JSLinearString* s, ClippedTime* result) {
  AutoCheckCannotGC nogc;
  return s->hasLatin1Chars()
             ? ParseDate(s->latin1Chars(nogc), s->length(), result)
             : ParseDate(s->twoByteChars(nogc), s->length(), result);
}

static bool date_parse(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  if (args.length() == 0) {
    args.rval().setNaN();
    return true;
  }

  JSString* str = ToString<CanGC>(cx, args[0]);
  if (!str) {
    return false;
  }

  JSLinearString* linearStr = str->ensureLinear(cx);
  if (!linearStr) {
    return false;
  }

  ClippedTime result;
  if (!ParseDate(linearStr, &result)) {
    args.rval().setNaN();
    return true;
  }

  args.rval().set(TimeValue(result));
  return true;
}

static ClippedTime NowAsMillis(JSContext* cx) {
  double now = PRMJ_Now();
  bool clampAndJitter = cx->realm()->behaviors().clampAndJitterTime();
  if (clampAndJitter && sReduceMicrosecondTimePrecisionCallback) {
    now = sReduceMicrosecondTimePrecisionCallback(now);
  } else if (clampAndJitter && sResolutionUsec) {
    double clamped = floor(now / sResolutionUsec) * sResolutionUsec;

    if (sJitter) {
      // Calculate a random midpoint for jittering. In the browser, we are
      // adversarial: Web Content may try to calculate the midpoint themselves
      // and use that to bypass it's security. In the JS Shell, we are not
      // adversarial, we want to jitter the time to recreate the operating
      // environment, but we do not concern ourselves with trying to prevent an
      // attacker from calculating the midpoint themselves. So we use a very
      // simple, very fast CRC with a hardcoded seed.

      uint64_t midpoint = BitwiseCast<uint64_t>(clamped);
      midpoint ^= 0x0F00DD1E2BAD2DED;  // XOR in a 'secret'
      // MurmurHash3 internal component from
      //   https://searchfox.org/mozilla-central/rev/61d400da1c692453c2dc2c1cf37b616ce13dea5b/dom/canvas/MurmurHash3.cpp#85
      midpoint ^= midpoint >> 33;
      midpoint *= uint64_t{0xFF51AFD7ED558CCD};
      midpoint ^= midpoint >> 33;
      midpoint *= uint64_t{0xC4CEB9FE1A85EC53};
      midpoint ^= midpoint >> 33;
      midpoint %= sResolutionUsec;

      if (now > clamped + midpoint) {  // We're jittering up to the next step
        now = clamped + sResolutionUsec;
      } else {  // We're staying at the clamped value
        now = clamped;
      }
    } else {  // No jitter, only clamping
      now = clamped;
    }
  }

  return TimeClip(now / PRMJ_USEC_PER_MSEC);
}

bool js::date_now(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  args.rval().set(TimeValue(NowAsMillis(cx)));
  return true;
}

void DateObject::setUTCTime(ClippedTime t) {
  for (size_t ind = COMPONENTS_START_SLOT; ind < RESERVED_SLOTS; ind++) {
    setReservedSlot(ind, UndefinedValue());
  }

  setFixedSlot(UTC_TIME_SLOT, TimeValue(t));
}

void DateObject::setUTCTime(ClippedTime t, MutableHandleValue vp) {
  setUTCTime(t);
  vp.set(TimeValue(t));
}

void DateObject::fillLocalTimeSlots() {
  const int32_t utcTZOffset = DateTimeInfo::utcToLocalStandardOffsetSeconds();

  /* Check if the cache is already populated. */
  if (!getReservedSlot(LOCAL_TIME_SLOT).isUndefined() &&
      getReservedSlot(UTC_TIME_ZONE_OFFSET_SLOT).toInt32() == utcTZOffset) {
    return;
  }

  /* Remember time zone used to generate the local cache. */
  setReservedSlot(UTC_TIME_ZONE_OFFSET_SLOT, Int32Value(utcTZOffset));

  double utcTime = UTCTime().toNumber();

  if (!IsFinite(utcTime)) {
    for (size_t ind = COMPONENTS_START_SLOT; ind < RESERVED_SLOTS; ind++) {
      setReservedSlot(ind, DoubleValue(utcTime));
    }
    return;
  }

  double localTime = LocalTime(utcTime);

  setReservedSlot(LOCAL_TIME_SLOT, DoubleValue(localTime));

  int year = (int)floor(localTime / (msPerDay * 365.2425)) + 1970;
  double yearStartTime = TimeFromYear(year);

  /* Adjust the year in case the approximation was wrong, as in YearFromTime. */
  int yearDays;
  if (yearStartTime > localTime) {
    year--;
    yearStartTime -= (msPerDay * DaysInYear(year));
    yearDays = DaysInYear(year);
  } else {
    yearDays = DaysInYear(year);
    double nextStart = yearStartTime + (msPerDay * yearDays);
    if (nextStart <= localTime) {
      year++;
      yearStartTime = nextStart;
      yearDays = DaysInYear(year);
    }
  }

  setReservedSlot(LOCAL_YEAR_SLOT, Int32Value(year));

  uint64_t yearTime = uint64_t(localTime - yearStartTime);
  int yearSeconds = uint32_t(yearTime / 1000);

  int day = yearSeconds / int(SecondsPerDay);

  int step = -1, next = 30;
  int month;

  do {
    if (day <= next) {
      month = 0;
      break;
    }
    step = next;
    next += ((yearDays == 366) ? 29 : 28);
    if (day <= next) {
      month = 1;
      break;
    }
    step = next;
    if (day <= (next += 31)) {
      month = 2;
      break;
    }
    step = next;
    if (day <= (next += 30)) {
      month = 3;
      break;
    }
    step = next;
    if (day <= (next += 31)) {
      month = 4;
      break;
    }
    step = next;
    if (day <= (next += 30)) {
      month = 5;
      break;
    }
    step = next;
    if (day <= (next += 31)) {
      month = 6;
      break;
    }
    step = next;
    if (day <= (next += 31)) {
      month = 7;
      break;
    }
    step = next;
    if (day <= (next += 30)) {
      month = 8;
      break;
    }
    step = next;
    if (day <= (next += 31)) {
      month = 9;
      break;
    }
    step = next;
    if (day <= (next += 30)) {
      month = 10;
      break;
    }
    step = next;
    month = 11;
  } while (0);

  setReservedSlot(LOCAL_MONTH_SLOT, Int32Value(month));
  setReservedSlot(LOCAL_DATE_SLOT, Int32Value(day - step));

  int weekday = WeekDay(localTime);
  setReservedSlot(LOCAL_DAY_SLOT, Int32Value(weekday));

  setReservedSlot(LOCAL_SECONDS_INTO_YEAR_SLOT, Int32Value(yearSeconds));
}

inline double DateObject::cachedLocalTime() {
  fillLocalTimeSlots();
  return getReservedSlot(LOCAL_TIME_SLOT).toDouble();
}

MOZ_ALWAYS_INLINE bool IsDate(HandleValue v) {
  return v.isObject() && v.toObject().is<DateObject>();
}

/*
 * See ECMA 15.9.5.4 thru 15.9.5.23
 */
/* static */ MOZ_ALWAYS_INLINE bool DateObject::getTime_impl(
    JSContext* cx, const CallArgs& args) {
  args.rval().set(args.thisv().toObject().as<DateObject>().UTCTime());
  return true;
}

static bool date_getTime(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getTime_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getYear_impl(
    JSContext* cx, const CallArgs& args) {
  DateObject* dateObj = &args.thisv().toObject().as<DateObject>();
  dateObj->fillLocalTimeSlots();

  Value yearVal = dateObj->getReservedSlot(LOCAL_YEAR_SLOT);
  if (yearVal.isInt32()) {
    /* Follow ECMA-262 to the letter, contrary to IE JScript. */
    int year = yearVal.toInt32() - 1900;
    args.rval().setInt32(year);
  } else {
    args.rval().set(yearVal);
  }

  return true;
}

static bool date_getYear(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getYear_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getFullYear_impl(
    JSContext* cx, const CallArgs& args) {
  DateObject* dateObj = &args.thisv().toObject().as<DateObject>();
  dateObj->fillLocalTimeSlots();

  args.rval().set(dateObj->getReservedSlot(LOCAL_YEAR_SLOT));
  return true;
}

static bool date_getFullYear(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getFullYear_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getUTCFullYear_impl(
    JSContext* cx, const CallArgs& args) {
  double result = args.thisv().toObject().as<DateObject>().UTCTime().toNumber();
  if (IsFinite(result)) {
    result = YearFromTime(result);
  }

  args.rval().setNumber(result);
  return true;
}

static bool date_getUTCFullYear(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getUTCFullYear_impl>(cx,
                                                                       args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getMonth_impl(
    JSContext* cx, const CallArgs& args) {
  DateObject* dateObj = &args.thisv().toObject().as<DateObject>();
  dateObj->fillLocalTimeSlots();

  args.rval().set(dateObj->getReservedSlot(LOCAL_MONTH_SLOT));
  return true;
}

static bool date_getMonth(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getMonth_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getUTCMonth_impl(
    JSContext* cx, const CallArgs& args) {
  double d = args.thisv().toObject().as<DateObject>().UTCTime().toNumber();
  args.rval().setNumber(MonthFromTime(d));
  return true;
}

static bool date_getUTCMonth(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getUTCMonth_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getDate_impl(
    JSContext* cx, const CallArgs& args) {
  DateObject* dateObj = &args.thisv().toObject().as<DateObject>();
  dateObj->fillLocalTimeSlots();

  args.rval().set(dateObj->getReservedSlot(LOCAL_DATE_SLOT));
  return true;
}

static bool date_getDate(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getDate_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getUTCDate_impl(
    JSContext* cx, const CallArgs& args) {
  double result = args.thisv().toObject().as<DateObject>().UTCTime().toNumber();
  if (IsFinite(result)) {
    result = DateFromTime(result);
  }

  args.rval().setNumber(result);
  return true;
}

static bool date_getUTCDate(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getUTCDate_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getDay_impl(
    JSContext* cx, const CallArgs& args) {
  DateObject* dateObj = &args.thisv().toObject().as<DateObject>();
  dateObj->fillLocalTimeSlots();

  args.rval().set(dateObj->getReservedSlot(LOCAL_DAY_SLOT));
  return true;
}

static bool date_getDay(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getDay_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getUTCDay_impl(
    JSContext* cx, const CallArgs& args) {
  double result = args.thisv().toObject().as<DateObject>().UTCTime().toNumber();
  if (IsFinite(result)) {
    result = WeekDay(result);
  }

  args.rval().setNumber(result);
  return true;
}

static bool date_getUTCDay(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getUTCDay_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getHours_impl(
    JSContext* cx, const CallArgs& args) {
  DateObject* dateObj = &args.thisv().toObject().as<DateObject>();
  dateObj->fillLocalTimeSlots();

  // Note: LOCAL_SECONDS_INTO_YEAR_SLOT is guaranteed to contain an
  // int32 or NaN after the call to fillLocalTimeSlots.
  Value yearSeconds = dateObj->getReservedSlot(LOCAL_SECONDS_INTO_YEAR_SLOT);
  if (yearSeconds.isDouble()) {
    MOZ_ASSERT(IsNaN(yearSeconds.toDouble()));
    args.rval().set(yearSeconds);
  } else {
    args.rval().setInt32((yearSeconds.toInt32() / int(SecondsPerHour)) %
                         int(HoursPerDay));
  }
  return true;
}

static bool date_getHours(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getHours_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getUTCHours_impl(
    JSContext* cx, const CallArgs& args) {
  double result = args.thisv().toObject().as<DateObject>().UTCTime().toNumber();
  if (IsFinite(result)) {
    result = HourFromTime(result);
  }

  args.rval().setNumber(result);
  return true;
}

static bool date_getUTCHours(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getUTCHours_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getMinutes_impl(
    JSContext* cx, const CallArgs& args) {
  DateObject* dateObj = &args.thisv().toObject().as<DateObject>();
  dateObj->fillLocalTimeSlots();

  // Note: LOCAL_SECONDS_INTO_YEAR_SLOT is guaranteed to contain an
  // int32 or NaN after the call to fillLocalTimeSlots.
  Value yearSeconds = dateObj->getReservedSlot(LOCAL_SECONDS_INTO_YEAR_SLOT);
  if (yearSeconds.isDouble()) {
    MOZ_ASSERT(IsNaN(yearSeconds.toDouble()));
    args.rval().set(yearSeconds);
  } else {
    args.rval().setInt32((yearSeconds.toInt32() / int(SecondsPerMinute)) %
                         int(MinutesPerHour));
  }
  return true;
}

static bool date_getMinutes(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getMinutes_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getUTCMinutes_impl(
    JSContext* cx, const CallArgs& args) {
  double result = args.thisv().toObject().as<DateObject>().UTCTime().toNumber();
  if (IsFinite(result)) {
    result = MinFromTime(result);
  }

  args.rval().setNumber(result);
  return true;
}

static bool date_getUTCMinutes(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getUTCMinutes_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getSeconds_impl(
    JSContext* cx, const CallArgs& args) {
  DateObject* dateObj = &args.thisv().toObject().as<DateObject>();
  dateObj->fillLocalTimeSlots();

  // Note: LOCAL_SECONDS_INTO_YEAR_SLOT is guaranteed to contain an
  // int32 or NaN after the call to fillLocalTimeSlots.
  Value yearSeconds = dateObj->getReservedSlot(LOCAL_SECONDS_INTO_YEAR_SLOT);
  if (yearSeconds.isDouble()) {
    MOZ_ASSERT(IsNaN(yearSeconds.toDouble()));
    args.rval().set(yearSeconds);
  } else {
    args.rval().setInt32(yearSeconds.toInt32() % int(SecondsPerMinute));
  }
  return true;
}

static bool date_getSeconds(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getSeconds_impl>(cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getUTCSeconds_impl(
    JSContext* cx, const CallArgs& args) {
  double result = args.thisv().toObject().as<DateObject>().UTCTime().toNumber();
  if (IsFinite(result)) {
    result = SecFromTime(result);
  }

  args.rval().setNumber(result);
  return true;
}

static bool date_getUTCSeconds(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getUTCSeconds_impl>(cx, args);
}

/*
 * Date.getMilliseconds is mapped to getUTCMilliseconds. As long as no
 * supported time zone has a fractional-second component, the differences in
 * their specifications aren't observable.
 *
 * The 'tz' database explicitly does not support fractional-second time zones.
 * For example the Netherlands observed Amsterdam Mean Time, estimated to be
 * UT +00:19:32.13, from 1909 to 1937, but in tzdata AMT is defined as exactly
 * UT +00:19:32.
 */

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getUTCMilliseconds_impl(
    JSContext* cx, const CallArgs& args) {
  double result = args.thisv().toObject().as<DateObject>().UTCTime().toNumber();
  if (IsFinite(result)) {
    result = msFromTime(result);
  }

  args.rval().setNumber(result);
  return true;
}

static bool date_getUTCMilliseconds(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getUTCMilliseconds_impl>(
      cx, args);
}

/* static */ MOZ_ALWAYS_INLINE bool DateObject::getTimezoneOffset_impl(
    JSContext* cx, const CallArgs& args) {
  DateObject* dateObj = &args.thisv().toObject().as<DateObject>();
  double utctime = dateObj->UTCTime().toNumber();
  double localtime = dateObj->cachedLocalTime();

  /*
   * Return the time zone offset in minutes for the current locale that is
   * appropriate for this time. This value would be a constant except for
   * daylight savings time.
   */
  double result = (utctime - localtime) / msPerMinute;
  args.rval().setNumber(result);
  return true;
}

static bool date_getTimezoneOffset(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, DateObject::getTimezoneOffset_impl>(cx,
                                                                          args);
}

MOZ_ALWAYS_INLINE bool date_setTime_impl(JSContext* cx, const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());
  if (args.length() == 0) {
    dateObj->setUTCTime(ClippedTime::invalid(), args.rval());
    return true;
  }

  double result;
  if (!ToNumber(cx, args[0], &result)) {
    return false;
  }

  dateObj->setUTCTime(TimeClip(result), args.rval());
  return true;
}

static bool date_setTime(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setTime_impl>(cx, args);
}

static bool GetMsecsOrDefault(JSContext* cx, const CallArgs& args, unsigned i,
                              double t, double* millis) {
  if (args.length() <= i) {
    *millis = msFromTime(t);
    return true;
  }
  return ToNumber(cx, args[i], millis);
}

static bool GetSecsOrDefault(JSContext* cx, const CallArgs& args, unsigned i,
                             double t, double* sec) {
  if (args.length() <= i) {
    *sec = SecFromTime(t);
    return true;
  }
  return ToNumber(cx, args[i], sec);
}

static bool GetMinsOrDefault(JSContext* cx, const CallArgs& args, unsigned i,
                             double t, double* mins) {
  if (args.length() <= i) {
    *mins = MinFromTime(t);
    return true;
  }
  return ToNumber(cx, args[i], mins);
}

/* ES6 20.3.4.23. */
MOZ_ALWAYS_INLINE bool date_setMilliseconds_impl(JSContext* cx,
                                                 const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  // Steps 1-2.
  double t = LocalTime(dateObj->UTCTime().toNumber());

  // Steps 3-4.
  double ms;
  if (!ToNumber(cx, args.get(0), &ms)) {
    return false;
  }

  // Step 5.
  double time = MakeTime(HourFromTime(t), MinFromTime(t), SecFromTime(t), ms);

  // Step 6.
  ClippedTime u = TimeClip(UTC(MakeDate(Day(t), time)));

  // Steps 7-8.
  dateObj->setUTCTime(u, args.rval());
  return true;
}

static bool date_setMilliseconds(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setMilliseconds_impl>(cx, args);
}

/* ES5 15.9.5.29. */
MOZ_ALWAYS_INLINE bool date_setUTCMilliseconds_impl(JSContext* cx,
                                                    const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  /* Step 1. */
  double t = dateObj->UTCTime().toNumber();

  /* Step 2. */
  double milli;
  if (!ToNumber(cx, args.get(0), &milli)) {
    return false;
  }
  double time =
      MakeTime(HourFromTime(t), MinFromTime(t), SecFromTime(t), milli);

  /* Step 3. */
  ClippedTime v = TimeClip(MakeDate(Day(t), time));

  /* Steps 4-5. */
  dateObj->setUTCTime(v, args.rval());
  return true;
}

static bool date_setUTCMilliseconds(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setUTCMilliseconds_impl>(cx, args);
}

/* ES5 15.9.5.30. */
MOZ_ALWAYS_INLINE bool date_setSeconds_impl(JSContext* cx,
                                            const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  // Steps 1-2.
  double t = LocalTime(dateObj->UTCTime().toNumber());

  // Steps 3-4.
  double s;
  if (!ToNumber(cx, args.get(0), &s)) {
    return false;
  }

  // Steps 5-6.
  double milli;
  if (!GetMsecsOrDefault(cx, args, 1, t, &milli)) {
    return false;
  }

  // Step 7.
  double date =
      MakeDate(Day(t), MakeTime(HourFromTime(t), MinFromTime(t), s, milli));

  // Step 8.
  ClippedTime u = TimeClip(UTC(date));

  // Step 9.
  dateObj->setUTCTime(u, args.rval());
  return true;
}

/* ES6 20.3.4.26. */
static bool date_setSeconds(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setSeconds_impl>(cx, args);
}

MOZ_ALWAYS_INLINE bool date_setUTCSeconds_impl(JSContext* cx,
                                               const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  /* Step 1. */
  double t = dateObj->UTCTime().toNumber();

  /* Step 2. */
  double s;
  if (!ToNumber(cx, args.get(0), &s)) {
    return false;
  }

  /* Step 3. */
  double milli;
  if (!GetMsecsOrDefault(cx, args, 1, t, &milli)) {
    return false;
  }

  /* Step 4. */
  double date =
      MakeDate(Day(t), MakeTime(HourFromTime(t), MinFromTime(t), s, milli));

  /* Step 5. */
  ClippedTime v = TimeClip(date);

  /* Steps 6-7. */
  dateObj->setUTCTime(v, args.rval());
  return true;
}

/* ES5 15.9.5.32. */
static bool date_setUTCSeconds(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setUTCSeconds_impl>(cx, args);
}

MOZ_ALWAYS_INLINE bool date_setMinutes_impl(JSContext* cx,
                                            const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  // Steps 1-2.
  double t = LocalTime(dateObj->UTCTime().toNumber());

  // Steps 3-4.
  double m;
  if (!ToNumber(cx, args.get(0), &m)) {
    return false;
  }

  // Steps 5-6.
  double s;
  if (!GetSecsOrDefault(cx, args, 1, t, &s)) {
    return false;
  }

  // Steps 7-8.
  double milli;
  if (!GetMsecsOrDefault(cx, args, 2, t, &milli)) {
    return false;
  }

  // Step 9.
  double date = MakeDate(Day(t), MakeTime(HourFromTime(t), m, s, milli));

  // Step 10.
  ClippedTime u = TimeClip(UTC(date));

  // Steps 11-12.
  dateObj->setUTCTime(u, args.rval());
  return true;
}

/* ES6 20.3.4.24. */
static bool date_setMinutes(JSContext* cx, unsigned argc, Value* vp) {
  // Steps 1-2 (the effectful parts).
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setMinutes_impl>(cx, args);
}

MOZ_ALWAYS_INLINE bool date_setUTCMinutes_impl(JSContext* cx,
                                               const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  /* Step 1. */
  double t = dateObj->UTCTime().toNumber();

  /* Step 2. */
  double m;
  if (!ToNumber(cx, args.get(0), &m)) {
    return false;
  }

  /* Step 3. */
  double s;
  if (!GetSecsOrDefault(cx, args, 1, t, &s)) {
    return false;
  }

  /* Step 4. */
  double milli;
  if (!GetMsecsOrDefault(cx, args, 2, t, &milli)) {
    return false;
  }

  /* Step 5. */
  double date = MakeDate(Day(t), MakeTime(HourFromTime(t), m, s, milli));

  /* Step 6. */
  ClippedTime v = TimeClip(date);

  /* Steps 7-8. */
  dateObj->setUTCTime(v, args.rval());
  return true;
}

/* ES5 15.9.5.34. */
static bool date_setUTCMinutes(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setUTCMinutes_impl>(cx, args);
}

MOZ_ALWAYS_INLINE bool date_setHours_impl(JSContext* cx, const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  // Steps 1-2.
  double t = LocalTime(dateObj->UTCTime().toNumber());

  // Steps 3-4.
  double h;
  if (!ToNumber(cx, args.get(0), &h)) {
    return false;
  }

  // Steps 5-6.
  double m;
  if (!GetMinsOrDefault(cx, args, 1, t, &m)) {
    return false;
  }

  // Steps 7-8.
  double s;
  if (!GetSecsOrDefault(cx, args, 2, t, &s)) {
    return false;
  }

  // Steps 9-10.
  double milli;
  if (!GetMsecsOrDefault(cx, args, 3, t, &milli)) {
    return false;
  }

  // Step 11.
  double date = MakeDate(Day(t), MakeTime(h, m, s, milli));

  // Step 12.
  ClippedTime u = TimeClip(UTC(date));

  // Steps 13-14.
  dateObj->setUTCTime(u, args.rval());
  return true;
}

/* ES5 15.9.5.35. */
static bool date_setHours(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setHours_impl>(cx, args);
}

MOZ_ALWAYS_INLINE bool date_setUTCHours_impl(JSContext* cx,
                                             const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  /* Step 1. */
  double t = dateObj->UTCTime().toNumber();

  /* Step 2. */
  double h;
  if (!ToNumber(cx, args.get(0), &h)) {
    return false;
  }

  /* Step 3. */
  double m;
  if (!GetMinsOrDefault(cx, args, 1, t, &m)) {
    return false;
  }

  /* Step 4. */
  double s;
  if (!GetSecsOrDefault(cx, args, 2, t, &s)) {
    return false;
  }

  /* Step 5. */
  double milli;
  if (!GetMsecsOrDefault(cx, args, 3, t, &milli)) {
    return false;
  }

  /* Step 6. */
  double newDate = MakeDate(Day(t), MakeTime(h, m, s, milli));

  /* Step 7. */
  ClippedTime v = TimeClip(newDate);

  /* Steps 8-9. */
  dateObj->setUTCTime(v, args.rval());
  return true;
}

/* ES5 15.9.5.36. */
static bool date_setUTCHours(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setUTCHours_impl>(cx, args);
}

MOZ_ALWAYS_INLINE bool date_setDate_impl(JSContext* cx, const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  /* Step 1. */
  double t = LocalTime(dateObj->UTCTime().toNumber());

  /* Step 2. */
  double date;
  if (!ToNumber(cx, args.get(0), &date)) {
    return false;
  }

  /* Step 3. */
  double newDate = MakeDate(MakeDay(YearFromTime(t), MonthFromTime(t), date),
                            TimeWithinDay(t));

  /* Step 4. */
  ClippedTime u = TimeClip(UTC(newDate));

  /* Steps 5-6. */
  dateObj->setUTCTime(u, args.rval());
  return true;
}

/* ES5 15.9.5.37. */
static bool date_setDate(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setDate_impl>(cx, args);
}

MOZ_ALWAYS_INLINE bool date_setUTCDate_impl(JSContext* cx,
                                            const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  /* Step 1. */
  double t = dateObj->UTCTime().toNumber();

  /* Step 2. */
  double date;
  if (!ToNumber(cx, args.get(0), &date)) {
    return false;
  }

  /* Step 3. */
  double newDate = MakeDate(MakeDay(YearFromTime(t), MonthFromTime(t), date),
                            TimeWithinDay(t));

  /* Step 4. */
  ClippedTime v = TimeClip(newDate);

  /* Steps 5-6. */
  dateObj->setUTCTime(v, args.rval());
  return true;
}

static bool date_setUTCDate(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setUTCDate_impl>(cx, args);
}

static bool GetDateOrDefault(JSContext* cx, const CallArgs& args, unsigned i,
                             double t, double* date) {
  if (args.length() <= i) {
    *date = DateFromTime(t);
    return true;
  }
  return ToNumber(cx, args[i], date);
}

static bool GetMonthOrDefault(JSContext* cx, const CallArgs& args, unsigned i,
                              double t, double* month) {
  if (args.length() <= i) {
    *month = MonthFromTime(t);
    return true;
  }
  return ToNumber(cx, args[i], month);
}

/* ES5 15.9.5.38. */
MOZ_ALWAYS_INLINE bool date_setMonth_impl(JSContext* cx, const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  /* Step 1. */
  double t = LocalTime(dateObj->UTCTime().toNumber());

  /* Step 2. */
  double m;
  if (!ToNumber(cx, args.get(0), &m)) {
    return false;
  }

  /* Step 3. */
  double date;
  if (!GetDateOrDefault(cx, args, 1, t, &date)) {
    return false;
  }

  /* Step 4. */
  double newDate =
      MakeDate(MakeDay(YearFromTime(t), m, date), TimeWithinDay(t));

  /* Step 5. */
  ClippedTime u = TimeClip(UTC(newDate));

  /* Steps 6-7. */
  dateObj->setUTCTime(u, args.rval());
  return true;
}

static bool date_setMonth(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setMonth_impl>(cx, args);
}

/* ES5 15.9.5.39. */
MOZ_ALWAYS_INLINE bool date_setUTCMonth_impl(JSContext* cx,
                                             const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  /* Step 1. */
  double t = dateObj->UTCTime().toNumber();

  /* Step 2. */
  double m;
  if (!ToNumber(cx, args.get(0), &m)) {
    return false;
  }

  /* Step 3. */
  double date;
  if (!GetDateOrDefault(cx, args, 1, t, &date)) {
    return false;
  }

  /* Step 4. */
  double newDate =
      MakeDate(MakeDay(YearFromTime(t), m, date), TimeWithinDay(t));

  /* Step 5. */
  ClippedTime v = TimeClip(newDate);

  /* Steps 6-7. */
  dateObj->setUTCTime(v, args.rval());
  return true;
}

static bool date_setUTCMonth(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setUTCMonth_impl>(cx, args);
}

static double ThisLocalTimeOrZero(Handle<DateObject*> dateObj) {
  double t = dateObj->UTCTime().toNumber();
  if (IsNaN(t)) {
    return +0;
  }
  return LocalTime(t);
}

static double ThisUTCTimeOrZero(Handle<DateObject*> dateObj) {
  double t = dateObj->as<DateObject>().UTCTime().toNumber();
  return IsNaN(t) ? +0 : t;
}

/* ES5 15.9.5.40. */
MOZ_ALWAYS_INLINE bool date_setFullYear_impl(JSContext* cx,
                                             const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  /* Step 1. */
  double t = ThisLocalTimeOrZero(dateObj);

  /* Step 2. */
  double y;
  if (!ToNumber(cx, args.get(0), &y)) {
    return false;
  }

  /* Step 3. */
  double m;
  if (!GetMonthOrDefault(cx, args, 1, t, &m)) {
    return false;
  }

  /* Step 4. */
  double date;
  if (!GetDateOrDefault(cx, args, 2, t, &date)) {
    return false;
  }

  /* Step 5. */
  double newDate = MakeDate(MakeDay(y, m, date), TimeWithinDay(t));

  /* Step 6. */
  ClippedTime u = TimeClip(UTC(newDate));

  /* Steps 7-8. */
  dateObj->setUTCTime(u, args.rval());
  return true;
}

static bool date_setFullYear(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setFullYear_impl>(cx, args);
}

/* ES5 15.9.5.41. */
MOZ_ALWAYS_INLINE bool date_setUTCFullYear_impl(JSContext* cx,
                                                const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  /* Step 1. */
  double t = ThisUTCTimeOrZero(dateObj);

  /* Step 2. */
  double y;
  if (!ToNumber(cx, args.get(0), &y)) {
    return false;
  }

  /* Step 3. */
  double m;
  if (!GetMonthOrDefault(cx, args, 1, t, &m)) {
    return false;
  }

  /* Step 4. */
  double date;
  if (!GetDateOrDefault(cx, args, 2, t, &date)) {
    return false;
  }

  /* Step 5. */
  double newDate = MakeDate(MakeDay(y, m, date), TimeWithinDay(t));

  /* Step 6. */
  ClippedTime v = TimeClip(newDate);

  /* Steps 7-8. */
  dateObj->setUTCTime(v, args.rval());
  return true;
}

static bool date_setUTCFullYear(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setUTCFullYear_impl>(cx, args);
}

/* ES5 Annex B.2.5. */
MOZ_ALWAYS_INLINE bool date_setYear_impl(JSContext* cx, const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());

  /* Step 1. */
  double t = ThisLocalTimeOrZero(dateObj);

  /* Step 2. */
  double y;
  if (!ToNumber(cx, args.get(0), &y)) {
    return false;
  }

  /* Step 3. */
  if (IsNaN(y)) {
    dateObj->setUTCTime(ClippedTime::invalid(), args.rval());
    return true;
  }

  /* Step 4. */
  double yint = ToInteger(y);
  if (0 <= yint && yint <= 99) {
    yint += 1900;
  }

  /* Step 5. */
  double day = MakeDay(yint, MonthFromTime(t), DateFromTime(t));

  /* Step 6. */
  double u = UTC(MakeDate(day, TimeWithinDay(t)));

  /* Steps 7-8. */
  dateObj->setUTCTime(TimeClip(u), args.rval());
  return true;
}

static bool date_setYear(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_setYear_impl>(cx, args);
}

/* constants for toString, toUTCString */
static const char* const days[] = {"Sun", "Mon", "Tue", "Wed",
                                   "Thu", "Fri", "Sat"};
static const char* const months[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
                                     "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};

/* ES5 B.2.6. */
MOZ_ALWAYS_INLINE bool date_toGMTString_impl(JSContext* cx,
                                             const CallArgs& args) {
  double utctime =
      args.thisv().toObject().as<DateObject>().UTCTime().toNumber();
  if (!IsFinite(utctime)) {
    args.rval().setString(cx->names().InvalidDate);
    return true;
  }

  char buf[100];
  SprintfLiteral(buf, "%s, %.2d %s %.4d %.2d:%.2d:%.2d GMT",
                 days[int(WeekDay(utctime))], int(DateFromTime(utctime)),
                 months[int(MonthFromTime(utctime))],
                 int(YearFromTime(utctime)), int(HourFromTime(utctime)),
                 int(MinFromTime(utctime)), int(SecFromTime(utctime)));

  JSString* str = NewStringCopyZ<CanGC>(cx, buf);
  if (!str) {
    return false;
  }

  args.rval().setString(str);
  return true;
}

static bool date_toGMTString(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_toGMTString_impl>(cx, args);
}

/* ES6 draft 2015-01-15 20.3.4.36. */
MOZ_ALWAYS_INLINE bool date_toISOString_impl(JSContext* cx,
                                             const CallArgs& args) {
  double utctime =
      args.thisv().toObject().as<DateObject>().UTCTime().toNumber();
  if (!IsFinite(utctime)) {
    JS_ReportErrorNumberASCII(cx, js::GetErrorMessage, nullptr,
                              JSMSG_INVALID_DATE);
    return false;
  }

  char buf[100];
  int year = int(YearFromTime(utctime));
  if (year < 0 || year > 9999) {
    SprintfLiteral(buf, "%+.6d-%.2d-%.2dT%.2d:%.2d:%.2d.%.3dZ",
                   int(YearFromTime(utctime)), int(MonthFromTime(utctime)) + 1,
                   int(DateFromTime(utctime)), int(HourFromTime(utctime)),
                   int(MinFromTime(utctime)), int(SecFromTime(utctime)),
                   int(msFromTime(utctime)));
  } else {
    SprintfLiteral(buf, "%.4d-%.2d-%.2dT%.2d:%.2d:%.2d.%.3dZ",
                   int(YearFromTime(utctime)), int(MonthFromTime(utctime)) + 1,
                   int(DateFromTime(utctime)), int(HourFromTime(utctime)),
                   int(MinFromTime(utctime)), int(SecFromTime(utctime)),
                   int(msFromTime(utctime)));
  }

  JSString* str = NewStringCopyZ<CanGC>(cx, buf);
  if (!str) {
    return false;
  }
  args.rval().setString(str);
  return true;
}

static bool date_toISOString(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_toISOString_impl>(cx, args);
}

/* ES5 15.9.5.44. */
static bool date_toJSON(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  /* Step 1. */
  RootedObject obj(cx, ToObject(cx, args.thisv()));
  if (!obj) {
    return false;
  }

  /* Step 2. */
  RootedValue tv(cx, ObjectValue(*obj));
  if (!ToPrimitive(cx, JSTYPE_NUMBER, &tv)) {
    return false;
  }

  /* Step 3. */
  if (tv.isDouble() && !IsFinite(tv.toDouble())) {
    args.rval().setNull();
    return true;
  }

  /* Step 4. */
  RootedValue toISO(cx);
  if (!GetProperty(cx, obj, obj, cx->names().toISOString, &toISO)) {
    return false;
  }

  /* Step 5. */
  if (!IsCallable(toISO)) {
    JS_ReportErrorNumberASCII(cx, js::GetErrorMessage, nullptr,
                              JSMSG_BAD_TOISOSTRING_PROP);
    return false;
  }

  /* Step 6. */
  return Call(cx, toISO, obj, args.rval());
}

#if ENABLE_INTL_API && !MOZ_SYSTEM_ICU
JSString* DateTimeHelper::timeZoneComment(JSContext* cx, double utcTime,
                                          double localTime) {
  const char* locale = cx->runtime()->getDefaultLocale();
  if (!locale) {
    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
                              JSMSG_DEFAULT_LOCALE_ERROR);
    return nullptr;
  }

  char16_t tzbuf[100];
  tzbuf[0] = ' ';
  tzbuf[1] = '(';

  char16_t* timeZoneStart = tzbuf + 2;
  constexpr size_t remainingSpace =
      mozilla::ArrayLength(tzbuf) - 2 - 1;  // for the trailing ')'

  int64_t utcMilliseconds = static_cast<int64_t>(utcTime);
  if (!DateTimeInfo::timeZoneDisplayName(timeZoneStart, remainingSpace,
                                         utcMilliseconds, locale)) {
    {
      JS_ReportOutOfMemory(cx);
    }
    return nullptr;
  }

  // Reject if the result string is empty.
  size_t len = js_strlen(timeZoneStart);
  if (len == 0) {
    return cx->names().empty;
  }

  // Parenthesize the returned display name.
  timeZoneStart[len] = ')';

  return NewStringCopyN<CanGC>(cx, tzbuf, 2 + len + 1);
}
#else
/* Interface to PRMJTime date struct. */
PRMJTime DateTimeHelper::toPRMJTime(double localTime, double utcTime) {
  double year = YearFromTime(localTime);

  PRMJTime prtm;
  prtm.tm_usec = int32_t(msFromTime(localTime)) * 1000;
  prtm.tm_sec = int8_t(SecFromTime(localTime));
  prtm.tm_min = int8_t(MinFromTime(localTime));
  prtm.tm_hour = int8_t(HourFromTime(localTime));
  prtm.tm_mday = int8_t(DateFromTime(localTime));
  prtm.tm_mon = int8_t(MonthFromTime(localTime));
  prtm.tm_wday = int8_t(WeekDay(localTime));
  prtm.tm_year = year;
  prtm.tm_yday = int16_t(DayWithinYear(localTime, year));
  prtm.tm_isdst = (daylightSavingTA(utcTime) != 0);

  return prtm;
}

size_t DateTimeHelper::formatTime(char* buf, size_t buflen, const char* fmt,
                                  double utcTime, double localTime) {
  PRMJTime prtm = toPRMJTime(localTime, utcTime);

  // If an equivalent year was used to compute the date/time components, use
  // the same equivalent year to determine the time zone name and offset in
  // PRMJ_FormatTime(...).
  int timeZoneYear = isRepresentableAsTime32(utcTime)
                         ? prtm.tm_year
                         : equivalentYearForDST(prtm.tm_year);
  int offsetInSeconds = (int)floor((localTime - utcTime) / msPerSecond);

  return PRMJ_FormatTime(buf, buflen, fmt, &prtm, timeZoneYear,
                         offsetInSeconds);
}

JSString* DateTimeHelper::timeZoneComment(JSContext* cx, double utcTime,
                                          double localTime) {
  char tzbuf[100];

  size_t tzlen = formatTime(tzbuf, sizeof tzbuf, " (%Z)", utcTime, localTime);
  if (tzlen != 0) {
    // Decide whether to use the resulting time zone string.
    //
    // Reject it if it contains any non-ASCII or non-printable characters.
    // It's then likely in some other character encoding, and we probably
    // won't display it correctly.
    bool usetz = true;
    for (size_t i = 0; i < tzlen; i++) {
      char16_t c = tzbuf[i];
      if (!IsAsciiPrintable(c)) {
        usetz = false;
        break;
      }
    }

    // Also reject it if it's not parenthesized or if it's ' ()'.
    if (tzbuf[0] != ' ' || tzbuf[1] != '(' || tzbuf[2] == ')') {
      usetz = false;
    }

    if (usetz) {
      return NewStringCopyN<CanGC>(cx, tzbuf, tzlen);
    }
  }

  return cx->names().empty;
}
#endif /* ENABLE_INTL_API && !MOZ_SYSTEM_ICU */

static JSString* TimeZoneComment(JSContext* cx, double utcTime,
                                 double localTime) {
  return DateTimeHelper::timeZoneComment(cx, utcTime, localTime);
}

enum class FormatSpec { DateTime, Date, Time };

static bool FormatDate(JSContext* cx, double utcTime, FormatSpec format,
                       MutableHandleValue rval) {
  if (!IsFinite(utcTime)) {
    rval.setString(cx->names().InvalidDate);
    return true;
  }

  MOZ_ASSERT(NumbersAreIdentical(TimeClip(utcTime).toDouble(), utcTime));

  double localTime = LocalTime(utcTime);

  int offset = 0;
  RootedString timeZoneComment(cx);
  if (format == FormatSpec::DateTime || format == FormatSpec::Time) {
    // Offset from GMT in minutes. The offset includes daylight savings,
    // if it applies.
    int minutes = (int)trunc((localTime - utcTime) / msPerMinute);

    // Map 510 minutes to 0830 hours.
    offset = (minutes / 60) * 100 + minutes % 60;

    // Print as "Wed Nov 05 1997 19:38:03 GMT-0800 (PST)".
    //
    // The TZA is printed as 'GMT-0800' rather than as 'PST' to avoid
    // operating-system dependence on strftime (which PRMJ_FormatTime
    // calls, for %Z only.) win32 prints PST as 'Pacific Standard Time.'
    // This way we always know what we're getting, and can parse it if
    // we produce it. The OS time zone string is included as a comment.
    //
    // When ICU is used to retrieve the time zone string, the localized
    // 'long' name format from CLDR is used. For example when the default
    // locale is "en-US", PST is displayed as 'Pacific Standard Time', but
    // when it is "ru", 'Тихоокеанское стандартное время' is used. This
    // also means the time zone string may not fit into Latin-1.

    // Get a time zone string from the OS or ICU to include as a comment.
    timeZoneComment = TimeZoneComment(cx, utcTime, localTime);
    if (!timeZoneComment) {
      return false;
    }
  }

  char buf[100];
  switch (format) {
    case FormatSpec::DateTime:
      /* Tue Oct 31 2000 09:41:40 GMT-0800 */
      SprintfLiteral(buf, "%s %s %.2d %.4d %.2d:%.2d:%.2d GMT%+.4d",
                     days[int(WeekDay(localTime))],
                     months[int(MonthFromTime(localTime))],
                     int(DateFromTime(localTime)), int(YearFromTime(localTime)),
                     int(HourFromTime(localTime)), int(MinFromTime(localTime)),
                     int(SecFromTime(localTime)), offset);
      break;
    case FormatSpec::Date:
      /* Tue Oct 31 2000 */
      SprintfLiteral(buf, "%s %s %.2d %.4d", days[int(WeekDay(localTime))],
                     months[int(MonthFromTime(localTime))],
                     int(DateFromTime(localTime)),
                     int(YearFromTime(localTime)));
      break;
    case FormatSpec::Time:
      /* 09:41:40 GMT-0800 */
      SprintfLiteral(buf, "%.2d:%.2d:%.2d GMT%+.4d",
                     int(HourFromTime(localTime)), int(MinFromTime(localTime)),
                     int(SecFromTime(localTime)), offset);
      break;
  }

  RootedString str(cx, NewStringCopyZ<CanGC>(cx, buf));
  if (!str) {
    return false;
  }

  // Append the time zone string if present.
  if (timeZoneComment && !timeZoneComment->empty()) {
    str = js::ConcatStrings<CanGC>(cx, str, timeZoneComment);
    if (!str) {
      return false;
    }
  }

  rval.setString(str);
  return true;
}

#if !ENABLE_INTL_API
static bool ToLocaleFormatHelper(JSContext* cx, HandleObject obj,
                                 const char* format, MutableHandleValue rval) {
  double utcTime = obj->as<DateObject>().UTCTime().toNumber();

  char buf[100];
  if (!IsFinite(utcTime)) {
    strcpy(buf, js_InvalidDate_str);
  } else {
    double localTime = LocalTime(utcTime);

    /* Let PRMJTime format it. */
    size_t result_len =
        DateTimeHelper::formatTime(buf, sizeof buf, format, utcTime, localTime);

    /* If it failed, default to toString. */
    if (result_len == 0) {
      return FormatDate(cx, utcTime, FormatSpec::DateTime, rval);
    }

    /* Hacked check against undesired 2-digit year 00/00/00 form. */
    if (strcmp(format, "%x") == 0 && result_len >= 6 &&
        /* Format %x means use OS settings, which may have 2-digit yr, so
           hack end of 3/11/22 or 11.03.22 or 11Mar22 to use 4-digit yr...*/
        !IsAsciiDigit(buf[result_len - 3]) &&
        IsAsciiDigit(buf[result_len - 2]) &&
        IsAsciiDigit(buf[result_len - 1]) &&
        /* ...but not if starts with 4-digit year, like 2022/3/11. */
        !(IsAsciiDigit(buf[0]) && IsAsciiDigit(buf[1]) &&
          IsAsciiDigit(buf[2]) && IsAsciiDigit(buf[3]))) {
      int year = int(YearFromTime(localTime));
      snprintf(buf + (result_len - 2), (sizeof buf) - (result_len - 2), "%d",
               year);
    }
  }

  if (cx->runtime()->localeCallbacks &&
      cx->runtime()->localeCallbacks->localeToUnicode) {
    return cx->runtime()->localeCallbacks->localeToUnicode(cx, buf, rval);
  }

  JSString* str = NewStringCopyZ<CanGC>(cx, buf);
  if (!str) {
    return false;
  }
  rval.setString(str);
  return true;
}

/* ES5 15.9.5.5. */
MOZ_ALWAYS_INLINE bool date_toLocaleString_impl(JSContext* cx,
                                                const CallArgs& args) {
  /*
   * Use '%#c' for windows, because '%c' is backward-compatible and non-y2k
   * with msvc; '%#c' requests that a full year be used in the result string.
   */
  static const char format[] =
#  if defined(_WIN32) && !defined(__MWERKS__)
      "%#c"
#  else
      "%c"
#  endif
      ;

  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());
  return ToLocaleFormatHelper(cx, dateObj, format, args.rval());
}

static bool date_toLocaleString(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_toLocaleString_impl>(cx, args);
}

/* ES5 15.9.5.6. */
MOZ_ALWAYS_INLINE bool date_toLocaleDateString_impl(JSContext* cx,
                                                    const CallArgs& args) {
  /*
   * Use '%#x' for windows, because '%x' is backward-compatible and non-y2k
   * with msvc; '%#x' requests that a full year be used in the result string.
   */
  static const char format[] =
#  if defined(_WIN32) && !defined(__MWERKS__)
      "%#x"
#  else
      "%x"
#  endif
      ;

  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());
  return ToLocaleFormatHelper(cx, dateObj, format, args.rval());
}

static bool date_toLocaleDateString(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_toLocaleDateString_impl>(cx, args);
}

/* ES5 15.9.5.7. */
MOZ_ALWAYS_INLINE bool date_toLocaleTimeString_impl(JSContext* cx,
                                                    const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());
  return ToLocaleFormatHelper(cx, dateObj, "%X", args.rval());
}

static bool date_toLocaleTimeString(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_toLocaleTimeString_impl>(cx, args);
}
#endif /* !ENABLE_INTL_API */

/* ES5 15.9.5.4. */
MOZ_ALWAYS_INLINE bool date_toTimeString_impl(JSContext* cx,
                                              const CallArgs& args) {
  return FormatDate(
      cx, args.thisv().toObject().as<DateObject>().UTCTime().toNumber(),
      FormatSpec::Time, args.rval());
}

static bool date_toTimeString(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_toTimeString_impl>(cx, args);
}

/* ES5 15.9.5.3. */
MOZ_ALWAYS_INLINE bool date_toDateString_impl(JSContext* cx,
                                              const CallArgs& args) {
  return FormatDate(
      cx, args.thisv().toObject().as<DateObject>().UTCTime().toNumber(),
      FormatSpec::Date, args.rval());
}

static bool date_toDateString(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_toDateString_impl>(cx, args);
}

MOZ_ALWAYS_INLINE bool date_toSource_impl(JSContext* cx, const CallArgs& args) {
  JSStringBuilder sb(cx);
  if (!sb.append("(new Date(") ||
      !NumberValueToStringBuffer(
          cx, args.thisv().toObject().as<DateObject>().UTCTime(), sb) ||
      !sb.append("))")) {
    return false;
  }

  JSString* str = sb.finishString();
  if (!str) {
    return false;
  }
  args.rval().setString(str);
  return true;
}

static bool date_toSource(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_toSource_impl>(cx, args);
}

// ES6 20.3.4.41.
MOZ_ALWAYS_INLINE bool date_toString_impl(JSContext* cx, const CallArgs& args) {
  // Steps 1-2.
  return FormatDate(
      cx, args.thisv().toObject().as<DateObject>().UTCTime().toNumber(),
      FormatSpec::DateTime, args.rval());
}

bool date_toString(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_toString_impl>(cx, args);
}

MOZ_ALWAYS_INLINE bool date_valueOf_impl(JSContext* cx, const CallArgs& args) {
  Rooted<DateObject*> dateObj(cx, &args.thisv().toObject().as<DateObject>());
  args.rval().set(dateObj->UTCTime());
  return true;
}

bool js::date_valueOf(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  return CallNonGenericMethod<IsDate, date_valueOf_impl>(cx, args);
}

// ES6 20.3.4.45 Date.prototype[@@toPrimitive]
static bool date_toPrimitive(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  // Steps 1-2.
  if (!args.thisv().isObject()) {
    ReportIncompatible(cx, args);
    return false;
  }

  // Steps 3-5.
  JSType hint;
  if (!GetFirstArgumentAsTypeHint(cx, args, &hint)) {
    return false;
  }
  if (hint == JSTYPE_UNDEFINED) {
    hint = JSTYPE_STRING;
  }

  args.rval().set(args.thisv());
  RootedObject obj(cx, &args.thisv().toObject());
  return OrdinaryToPrimitive(cx, obj, hint, args.rval());
}

static const JSFunctionSpec date_static_methods[] = {
    JS_FN("UTC", date_UTC, 7, 0), JS_FN("parse", date_parse, 1, 0),
    JS_FN("now", date_now, 0, 0), JS_FS_END};

static const JSFunctionSpec date_methods[] = {
    JS_FN("getTime", date_getTime, 0, 0),
    JS_FN("getTimezoneOffset", date_getTimezoneOffset, 0, 0),
    JS_FN("getYear", date_getYear, 0, 0),
    JS_FN("getFullYear", date_getFullYear, 0, 0),
    JS_FN("getUTCFullYear", date_getUTCFullYear, 0, 0),
    JS_FN("getMonth", date_getMonth, 0, 0),
    JS_FN("getUTCMonth", date_getUTCMonth, 0, 0),
    JS_FN("getDate", date_getDate, 0, 0),
    JS_FN("getUTCDate", date_getUTCDate, 0, 0),
    JS_FN("getDay", date_getDay, 0, 0),
    JS_FN("getUTCDay", date_getUTCDay, 0, 0),
    JS_FN("getHours", date_getHours, 0, 0),
    JS_FN("getUTCHours", date_getUTCHours, 0, 0),
    JS_FN("getMinutes", date_getMinutes, 0, 0),
    JS_FN("getUTCMinutes", date_getUTCMinutes, 0, 0),
    JS_FN("getSeconds", date_getSeconds, 0, 0),
    JS_FN("getUTCSeconds", date_getUTCSeconds, 0, 0),
    JS_FN("getMilliseconds", date_getUTCMilliseconds, 0, 0),
    JS_FN("getUTCMilliseconds", date_getUTCMilliseconds, 0, 0),
    JS_FN("setTime", date_setTime, 1, 0),
    JS_FN("setYear", date_setYear, 1, 0),
    JS_FN("setFullYear", date_setFullYear, 3, 0),
    JS_FN("setUTCFullYear", date_setUTCFullYear, 3, 0),
    JS_FN("setMonth", date_setMonth, 2, 0),
    JS_FN("setUTCMonth", date_setUTCMonth, 2, 0),
    JS_FN("setDate", date_setDate, 1, 0),
    JS_FN("setUTCDate", date_setUTCDate, 1, 0),
    JS_FN("setHours", date_setHours, 4, 0),
    JS_FN("setUTCHours", date_setUTCHours, 4, 0),
    JS_FN("setMinutes", date_setMinutes, 3, 0),
    JS_FN("setUTCMinutes", date_setUTCMinutes, 3, 0),
    JS_FN("setSeconds", date_setSeconds, 2, 0),
    JS_FN("setUTCSeconds", date_setUTCSeconds, 2, 0),
    JS_FN("setMilliseconds", date_setMilliseconds, 1, 0),
    JS_FN("setUTCMilliseconds", date_setUTCMilliseconds, 1, 0),
    JS_FN("toUTCString", date_toGMTString, 0, 0),
#if ENABLE_INTL_API
    JS_SELF_HOSTED_FN(js_toLocaleString_str, "Date_toLocaleString", 0, 0),
    JS_SELF_HOSTED_FN("toLocaleDateString", "Date_toLocaleDateString", 0, 0),
    JS_SELF_HOSTED_FN("toLocaleTimeString", "Date_toLocaleTimeString", 0, 0),
#else
    JS_FN(js_toLocaleString_str, date_toLocaleString, 0, 0),
    JS_FN("toLocaleDateString", date_toLocaleDateString, 0, 0),
    JS_FN("toLocaleTimeString", date_toLocaleTimeString, 0, 0),
#endif
    JS_FN("toDateString", date_toDateString, 0, 0),
    JS_FN("toTimeString", date_toTimeString, 0, 0),
    JS_FN("toISOString", date_toISOString, 0, 0),
    JS_FN(js_toJSON_str, date_toJSON, 1, 0),
    JS_FN(js_toSource_str, date_toSource, 0, 0),
    JS_FN(js_toString_str, date_toString, 0, 0),
    JS_FN(js_valueOf_str, date_valueOf, 0, 0),
    JS_SYM_FN(toPrimitive, date_toPrimitive, 1, JSPROP_READONLY),
    JS_FS_END};

static bool NewDateObject(JSContext* cx, const CallArgs& args, ClippedTime t) {
  MOZ_ASSERT(args.isConstructing());

  RootedObject proto(cx);
  if (!GetPrototypeFromBuiltinConstructor(cx, args, JSProto_Date, &proto)) {
    return false;
  }

  JSObject* obj = NewDateObjectMsec(cx, t, proto);
  if (!obj) {
    return false;
  }

  args.rval().setObject(*obj);
  return true;
}

static bool ToDateString(JSContext* cx, const CallArgs& args, ClippedTime t) {
  return FormatDate(cx, t.toDouble(), FormatSpec::DateTime, args.rval());
}

static bool DateNoArguments(JSContext* cx, const CallArgs& args) {
  MOZ_ASSERT(args.length() == 0);

  ClippedTime now = NowAsMillis(cx);

  if (args.isConstructing()) {
    return NewDateObject(cx, args, now);
  }

  return ToDateString(cx, args, now);
}

static bool DateOneArgument(JSContext* cx, const CallArgs& args) {
  MOZ_ASSERT(args.length() == 1);

  if (args.isConstructing()) {
    if (args[0].isObject()) {
      RootedObject obj(cx, &args[0].toObject());

      ESClass cls;
      if (!GetBuiltinClass(cx, obj, &cls)) {
        return false;
      }

      if (cls == ESClass::Date) {
        RootedValue unboxed(cx);
        if (!Unbox(cx, obj, &unboxed)) {
          return false;
        }

        return NewDateObject(cx, args, TimeClip(unboxed.toNumber()));
      }
    }

    if (!ToPrimitive(cx, args[0])) {
      return false;
    }

    ClippedTime t;
    if (args[0].isString()) {
      JSLinearString* linearStr = args[0].toString()->ensureLinear(cx);
      if (!linearStr) {
        return false;
      }

      if (!ParseDate(linearStr, &t)) {
        t = ClippedTime::invalid();
      }
    } else {
      double d;
      if (!ToNumber(cx, args[0], &d)) {
        return false;
      }
      t = TimeClip(d);
    }

    return NewDateObject(cx, args, t);
  }

  return ToDateString(cx, args, NowAsMillis(cx));
}

static bool DateMultipleArguments(JSContext* cx, const CallArgs& args) {
  MOZ_ASSERT(args.length() >= 2);

  // Step 3.
  if (args.isConstructing()) {
    // Steps 3a-b.
    double y;
    if (!ToNumber(cx, args[0], &y)) {
      return false;
    }

    // Steps 3c-d.
    double m;
    if (!ToNumber(cx, args[1], &m)) {
      return false;
    }

    // Steps 3e-f.
    double dt;
    if (args.length() >= 3) {
      if (!ToNumber(cx, args[2], &dt)) {
        return false;
      }
    } else {
      dt = 1;
    }

    // Steps 3g-h.
    double h;
    if (args.length() >= 4) {
      if (!ToNumber(cx, args[3], &h)) {
        return false;
      }
    } else {
      h = 0;
    }

    // Steps 3i-j.
    double min;
    if (args.length() >= 5) {
      if (!ToNumber(cx, args[4], &min)) {
        return false;
      }
    } else {
      min = 0;
    }

    // Steps 3k-l.
    double s;
    if (args.length() >= 6) {
      if (!ToNumber(cx, args[5], &s)) {
        return false;
      }
    } else {
      s = 0;
    }

    // Steps 3m-n.
    double milli;
    if (args.length() >= 7) {
      if (!ToNumber(cx, args[6], &milli)) {
        return false;
      }
    } else {
      milli = 0;
    }

    // Step 3o.
    double yr = y;
    if (!IsNaN(y)) {
      double yint = ToInteger(y);
      if (0 <= yint && yint <= 99) {
        yr = 1900 + yint;
      }
    }

    // Step 3p.
    double finalDate = MakeDate(MakeDay(yr, m, dt), MakeTime(h, min, s, milli));

    // Steps 3q-t.
    return NewDateObject(cx, args, TimeClip(UTC(finalDate)));
  }

  return ToDateString(cx, args, NowAsMillis(cx));
}

static bool DateConstructor(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  if (args.length() == 0) {
    return DateNoArguments(cx, args);
  }

  if (args.length() == 1) {
    return DateOneArgument(cx, args);
  }

  return DateMultipleArguments(cx, args);
}

static bool FinishDateClassInit(JSContext* cx, HandleObject ctor,
                                HandleObject proto) {
  /*
   * Date.prototype.toGMTString has the same initial value as
   * Date.prototype.toUTCString.
   */
  RootedValue toUTCStringFun(cx);
  RootedId toUTCStringId(cx, NameToId(cx->names().toUTCString));
  RootedId toGMTStringId(cx, NameToId(cx->names().toGMTString));
  return NativeGetProperty(cx, proto.as<NativeObject>(), toUTCStringId,
                           &toUTCStringFun) &&
         NativeDefineDataProperty(cx, proto.as<NativeObject>(), toGMTStringId,
                                  toUTCStringFun, 0);
}

static const ClassSpec DateObjectClassSpec = {
    GenericCreateConstructor<DateConstructor, 7, gc::AllocKind::FUNCTION>,
    GenericCreatePrototype<DateObject>,
    date_static_methods,
    nullptr,
    date_methods,
    nullptr,
    FinishDateClassInit};

const JSClass DateObject::class_ = {js_Date_str,
                                    JSCLASS_HAS_RESERVED_SLOTS(RESERVED_SLOTS) |
                                        JSCLASS_HAS_CACHED_PROTO(JSProto_Date),
                                    JS_NULL_CLASS_OPS, &DateObjectClassSpec};

const JSClass DateObject::protoClass_ = {
    js_Object_str, JSCLASS_HAS_CACHED_PROTO(JSProto_Date), JS_NULL_CLASS_OPS,
    &DateObjectClassSpec};

JSObject* js::NewDateObjectMsec(JSContext* cx, ClippedTime t,
                                HandleObject proto /* = nullptr */) {
  DateObject* obj = NewObjectWithClassProto<DateObject>(cx, proto);
  if (!obj) {
    return nullptr;
  }
  obj->setUTCTime(t);
  return obj;
}

JS_PUBLIC_API JSObject* JS::NewDateObject(JSContext* cx, ClippedTime time) {
  AssertHeapIsIdle();
  CHECK_THREAD(cx);
  return NewDateObjectMsec(cx, time);
}

JS_FRIEND_API JSObject* js::NewDateObject(JSContext* cx, int year, int mon,
                                          int mday, int hour, int min,
                                          int sec) {
  MOZ_ASSERT(mon < 12);
  double msec_time =
      MakeDate(MakeDay(year, mon, mday), MakeTime(hour, min, sec, 0.0));
  return NewDateObjectMsec(cx, TimeClip(UTC(msec_time)));
}

JS_FRIEND_API bool js::DateIsValid(JSContext* cx, HandleObject obj,
                                   bool* isValid) {
  ESClass cls;
  if (!GetBuiltinClass(cx, obj, &cls)) {
    return false;
  }

  if (cls != ESClass::Date) {
    *isValid = false;
    return true;
  }

  RootedValue unboxed(cx);
  if (!Unbox(cx, obj, &unboxed)) {
    return false;
  }

  *isValid = !IsNaN(unboxed.toNumber());
  return true;
}

JS_PUBLIC_API JSObject* JS::NewDateObject(JSContext* cx, int year, int mon,
                                          int mday, int hour, int min,
                                          int sec) {
  AssertHeapIsIdle();
  CHECK_THREAD(cx);
  return js::NewDateObject(cx, year, mon, mday, hour, min, sec);
}

JS_PUBLIC_API bool JS::ObjectIsDate(JSContext* cx, Handle<JSObject*> obj,
                                    bool* isDate) {
  cx->check(obj);

  ESClass cls;
  if (!GetBuiltinClass(cx, obj, &cls)) {
    return false;
  }

  *isDate = cls == ESClass::Date;
  return true;
}

JS_FRIEND_API bool js::DateGetMsecSinceEpoch(JSContext* cx, HandleObject obj,
                                             double* msecsSinceEpoch) {
  ESClass cls;
  if (!GetBuiltinClass(cx, obj, &cls)) {
    return false;
  }

  if (cls != ESClass::Date) {
    *msecsSinceEpoch = 0;
    return true;
  }

  RootedValue unboxed(cx);
  if (!Unbox(cx, obj, &unboxed)) {
    return false;
  }

  *msecsSinceEpoch = unboxed.toNumber();
  return true;
}