code: def openTypeHeadCreatedFallback(info):
      
      if "SOURCE_DATE_EPOCH" in os.environ:
          t = datetime.utcfromtimestamp(int(os.environ["SOURCE_DATE_EPOCH"]))
          return t.strftime(_date_format)
      else:
          return dateStringForNow()
docs: Fallback to the environment variable SOURCE_DATE_EPOCH if set, otherwise
      now.