docs: def parse_date_period(date):
      """
      Parse the --date value and return a couple of datetime object.
      The format is [YYYY]MMDD[,[YYYY]MMDD].
      """
      import datetime
      
      now = datetime.datetime.today()
      date_len = len(date)
      
      if date_len == 4:
          date1 = str(now.year) + date
          date2 = str(now.year) + date + "235959"
      elif date_len == 8:
          date1 = date
          date2 = date + "235959"
      elif date_len == 9:
          if date[4] != ',':
              raise TypeError
          date1 = str(now.year) + date[0:4]
          date2 = str(now.year) + date[5:9] + "235959"
      elif date_len == 17:
          if date[8] != ',':
              raise TypeError
          date1 = date[0:8]
          date2 = date[9:17] + "235959"
      else:
          raise TypeError
  
      try:
          date1 = datetime.datetime.strptime(date1, "%Y%m%d")
      except ValueError:
          if date_len < 9:
              raise ValueError("Error of date value in --date parameter, use --date=[YYYY]MMDD")
          else:
              raise ValueError("Error in the first date value in --date parameter, "
                               "use --date=[YYYY]MMDD,[YYYY]MMDD")
      try:
          date2 = datetime.datetime.strptime(date2, "%Y%m%d%H%M%S")        
      except ValueError:
          raise ValueError("Error in the second date value in --date parameter, "
                           "use --date=[YYYY]MMDD,[YYYY]MMDD")
          
      if date1 > date2:
          raise ValueError("Wrong parameter --date: the first date is after the second!")
  
      return date1, date2