docs: def guess_datetime(datetime_string):
      """Try to guess the datetime contained in a string of unknow format.
  
      @param datetime_string: the datetime representation.
      @type datetime_string: string
      @return: the guessed time.
      @rtype: L{time.struct_time}
      @raises ValueError: in case it's not possible to guess the time.
      """
      if CFG_HAS_EGENIX_DATETIME:
          try:
              return Parser.DateTimeFromString(datetime_string).timetuple()
          except ValueError:
              pass
      else:
          for format in (None, '%x %X', '%X %x', '%Y-%M-%dT%h:%m:%sZ'):
              try:
                  return time.strptime(datetime_string, format)
              except ValueError:
                  pass
      raise ValueError("It is not possible to guess the datetime format of %s" %
                       datetime_string)