Provided is an electronic clock including: a power generator; a secondary battery, which is to be charged with electric power generated by the power generator; a balance information transmitter configured to transmit, to a computer, balance information relating to a transition of a power generation amount or a charging balance of the secondary battery; a connection time period setting module configured to set a connection time period of a connection with the computer based on the balance information; and a communication controller configured to control a start and an end of communication to/from the computer based on the connection time period.