new_contents: 
  # Copyright 2020 John Hanley.
  #
  # Permission is hereby granted, free of charge, to any person obtaining a
  # copy of this software and associated documentation files (the "Software"),
  # to deal in the Software without restriction, including without limitation
  # the rights to use, copy, modify, merge, publish, distribute, sublicense,
  # and/or sell copies of the Software, and to permit persons to whom the
  # Software is furnished to do so, subject to the following conditions:
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
  # The software is provided "AS IS", without warranty of any kind, express or
  # implied, including but not limited to the warranties of merchantability,
  # fitness for a particular purpose and noninfringement. In no event shall
  # the authors or copyright holders be liable for any claim, damages or
  # other liability, whether in an action of contract, tort or otherwise,
  # arising from, out of or in connection with the software or the use or
  # other dealings in the software.
  
  import datetime as dt
  
  
  class Datetimez(dt.datetime):
      """Supports _always_ using UTC."""
  
      utc = dt.timezone.utc
  
      @classmethod
      def from_(cls, datetime: dt.datetime):
          return datetime.replace(tzinfo=cls.utc)
  
      @classmethod
      def fromisoformat(cls, date_string: str):
          assert date_string.endswith("+0000"), date_string
          return (super().fromisoformat(date_string.replace("+0000", ""))
                  .replace(tzinfo=cls.utc))
  
      @classmethod
      def fromtimestamp(cls, sec):
          return super().fromtimestamp(sec).replace(tzinfo=cls.utc)
  
      @classmethod
      def now(cls):
          return super().now().replace(tzinfo=cls.utc)
  
      @classmethod
      def strptime(cls, date_string, format):
          return super().strptime(date_string, format).replace(tzinfo=cls.utc)
  
subject: Add datetimez.