code: def validate_day_start_ut(conn):
      
      G = GTFS(conn)
      cur = conn.execute('SELECT date, day_start_ut FROM days')
      for date, day_start_ut in cur:
          #print date, day_start_ut
          assert day_start_ut == G.get_day_start_ut(date)
docs: This validates the day_start_ut of the days table.