[Findit] For automatic analyses of flaky tests, run the Swarming tasks off PST peak hours.

appengine/findit/common/time_util.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import calendar
 from datetime import datetime
 from datetime import time
 from datetime import timedelta
 
+import pytz
+
 
 def GetUTCNow():  # pragma: no cover.
   """Returns the datetime.utcnow. This is to mock for testing."""
   return datetime.utcnow()
 
 
+def GetUTCNowWithTimezone():  # pragma: no cover.
+  """Returns datetime.now but in utc timezone. This is to mock for testing."""
+  return datetime.now(pytz.utc)
+
+
 def GetUTCNowTimestamp():  # pragma: no cover.
   """Returns the timestamp for datetime.utcnow. This is to mock for testing."""
   return calendar.timegm(GetUTCNow().timetuple())
 
 
 def RemoveMicrosecondsFromDelta(delta):
   """Returns a timedelta object without microseconds based on delta."""
   return delta - timedelta(microseconds=delta.microseconds)
 
 
 def FormatTimedelta(delta):
   if not delta:
     return None
   hours, remainder = divmod(delta.seconds, 3600)
   minutes, seconds = divmod(remainder, 60)
   return '%02d:%02d:%02d' % (hours, minutes, seconds)
 
 
 def FormatDatetime(date):
   if not date:
     return None
   else:
     return date.strftime('%Y-%m-%d %H:%M:%S UTC')
+
+
+def GetDatetimeInTimezone(timezone_name, date_time=None):
+  """Returns the datetime.datetime of the given one in the specified timezone.
+
+  Args:
+    timezone_name (str): The name of any timezone supported by pytz.
+    date_time (datetime.datetime): The optional datetime to be converted into
+        the new timezone. If not given, default to UTC now.

[lijeffrey, 2016/09/27 23:48:05]

Is there a reason we don't just pass the default
date_time=GetUTCNowWithTimezone()?

i.e.
def GetDatetimeInTimezone(timezone_name, date_time=GetUTCNowWithTimezone()):
  ...

[stgao, 2016/10/01 05:55:25]

No, we can't.
Default value is created and set once and then used afterwards.
For time, it depends on when the function is called.

+
+  Returns:
+    A datetime.datetime of the given one in the specified timezone.
+  """
+  date_time = date_time or GetUTCNowWithTimezone()
+  return date_time.astimezone(pytz.timezone(timezone_name))