code: def _total_microsec(t1, t2):
      
      td = t1 - t2
      return (td.seconds + td.days * 24 * 3600) * 10 ** 6 + td.microseconds
docs: Calculate difference between two datetime stamps in microseconds.
  
      :type t1: :class: `datetime.datetime`
      :type t2: :class: `datetime.datetime`
      :return: int
  
      .. rubric:: Example
  
      >>> print(_total_microsec(UTCDateTime(2013, 1, 1).datetime,
      ...                       UTCDateTime(2014, 1, 1).datetime))
      -31536000000000