--- a/mozilla/project_branches.py
+++ b/mozilla/project_branches.py
@@ -26,17 +26,17 @@ PROJECT_BRANCHES = {
     #'services-central': {},  # Bug 1010674
     # 'alder': {},
     # Bug 1252292 - Schedule e10s tests on Ash for all desktop platforms
     'ash': {
         'enable_talos': False,
         'enable_valgrind': False,
         'lock_platforms': True,
         'merge_builds': False,
-        'periodic_start_hours': range(9, 0, 12),
+        'periodic_start_hours': [9, 21],
         'pgo_strategy': 'periodic',
         'platforms': {
             'linux': {
                 'slave_platforms': ['ubuntu32_vm'],
             },
             'linux-debug': {
                 'slave_platforms': ['ubuntu32_vm'],
             },