text: #!/usr/bin/env python
  # Copyright 2018 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.
  #
  # copied from chromium.
  
  """Returns a timestamp that approximates the build date.
  
  build_type impacts the timestamp generated, both relative to the date of the
  last recent commit:
  - default: the build date is set to the most recent first Sunday of a month at
    5:00am. The reason is that it is a time where invalidating the build cache
    shouldn't have major reprecussions (due to lower load).
  - official: the build date is set to the current date at 5:00am, or the day
    before if the current time is before 5:00am.
  Either way, it is guaranteed to be in the past and always in UTC.
  """
  
  # The requirements for the timestamp:
  # (1) for the purposes of continuous integration, longer duration
  #     between cache invalidation is better, but >=1mo is preferable.
  # (2) for security purposes, timebombs would ideally be as close to
  #     the actual time of the build as possible. It must be in the past.
  # (3) HSTS certificate pinning is valid for 70 days. To make CI builds enforce
  #     HTST pinning, <=1mo is preferable.
  #
  # On Windows, the timestamp is also written in the PE/COFF file header of
  # executables of dlls.  That timestamp and the executable's file size are
  # the only two pieces of information that identify a given executable on
  # the symbol server, so rarely changing timestamps can cause conflicts there
  # as well. We only upload symbols for official builds to the symbol server.
  
  import argparse
  import calendar
  import datetime
  import doctest
  import os
  import sys
  
  
  THIS_DIR = os.path.abspath(os.path.dirname(__file__))
  
  
  def GetFirstSundayOfMonth(year, month):
    """Returns the first sunday of the given month of the given year.
  
    >>> GetFirstSundayOfMonth(2016, 2)
    7
    >>> GetFirstSundayOfMonth(2016, 3)
    6
    >>> GetFirstSundayOfMonth(2000, 1)
    2
    """
    weeks = calendar.Calendar().monthdays2calendar(year, month)
    # Return the first day in the first week that is a Sunday.
    return [date_day[0] for date_day in weeks[0] if date_day[1] == 6][0]
  
  
  def GetBuildDate(build_type, utc_now):
    """Gets the approximate build date given the specific build type.
  
    >>> GetBuildDate('default', datetime.datetime(2016, 2, 6, 1, 2, 3))
    datetime.datetime(2016, 1, 3, 1, 2, 3)
    >>> GetBuildDate('default', datetime.datetime(2016, 2, 7, 5))
    datetime.datetime(2016, 2, 7, 5, 0)
    >>> GetBuildDate('default', datetime.datetime(2016, 2, 8, 5))
    datetime.datetime(2016, 2, 7, 5, 0)
    >>> GetBuildDate('official', datetime.datetime(2016, 2, 8, 5))
    datetime.datetime(2016, 2, 8, 5, 0)
    """
    day = utc_now.day
    month = utc_now.month
    year = utc_now.year
    if build_type != 'official':
      first_sunday = GetFirstSundayOfMonth(year, month)
      # If our build is after the first Sunday, we've already refreshed our build
      # cache on a quiet day, so just use that day.
      # Otherwise, take the first Sunday of the previous month.
      if day >= first_sunday:
        day = first_sunday
      else:
        month -= 1
        if month == 0:
          month = 12
          year -= 1
        day = GetFirstSundayOfMonth(year, month)
    return datetime.datetime(
        year, month, day, utc_now.hour, utc_now.minute, utc_now.second)
  
  
  def main():
    if doctest.testmod()[0]:
      return 1
    argument_parser = argparse.ArgumentParser()
    argument_parser.add_argument(
        'build_type', help='The type of build', choices=('official', 'default'))
    args = argument_parser.parse_args()
  
    # The mtime of the revision in build/util/LASTCHANGE is stored in a file
    # next to it. Read it, to get a deterministic time close to "now".
    # That date is then modified as described at the top of the file so that
    # it changes less frequently than with every commit.
    # This intentionally always uses build/util/LASTCHANGE's commit time even if
    # use_dummy_lastchange is set.
    lastchange_file = os.path.join(THIS_DIR, 'util', 'LASTCHANGE.committime')
    last_commit_timestamp = int(open(lastchange_file).read())
    now = datetime.datetime.utcfromtimestamp(last_commit_timestamp)
  
    if now.hour < 5:
      # The time is locked at 5:00 am in UTC to cause the build cache
      # invalidation to not happen exactly at midnight. Use the same calculation
      # as the day before.
      # See //base/build_time.cc.
      now = now - datetime.timedelta(days=1)
    now = datetime.datetime(now.year, now.month, now.day, 5, 0, 0)
    build_date = GetBuildDate(args.build_type, now)
    print int(calendar.timegm(build_date.utctimetuple()))
    return 0
  
  
  if __name__ == '__main__':
    sys.exit(main())
  