PURPOSE: To highly accurately stabilize a watch by compensating the frequency fluctuations in the time reference signals which are generated as a result of the potential variations during the charge and discharge of a secondary battery.

CONSTITUTION: When the discharge of a secondary battery 12 exceeds 30 % so that the battery potential is lowered to reduce the output signals of a voltage detecting circuit 12 to "0", an auxiliary frequency dividing circuit 4 is reset, and the time reference signals from an oscillating circuit 1 are subjected to frequency division through a transmission gate 2 by a frequency dividing circuit 5 thereby to display the time in a display unit 8. When the secondary battery 12 bigins to be charged by the optical irradiation upon a solar cell 9 to increase the output signals of the circuit 12 to "1", the auxiliary circuit 4 takes its frequency division starting condition so that a transmission gate 3 becomes conductive. Since the oscillatory frequency of the circuit 1 is subjected to the frequency division by the circuit 4 and then by the circuit 5, the frequency increment due to the rise in the voltage of the secondary battery is counted by the auxiliary circuit 4 so that accurate time reference signals can be generated at the output of the circuit 5.