To correct efficiently the date and time clocked by a meter to a standard date and time.

The meter 10 transmits the date and time clocked by a clock part 15 to a management terminal 20 in response to a date-and-time confirmation request sent from the management terminal 20 connected through a network 30. The management terminal 20 calculates an error between the date and time clocked by the clock part 15 sent from the meter 10 and the date and time managed by a standard clock part 25, and transmits the standard date and time to the meter 10 only when the error is determined to be larger than a prescribed value. The meter 10 corrects the date and time clocked by the clock part 15 to the sent standard date and time.