To set time on an RTC (real time clock) not holding time for digits of shorter than a second with an accuracy shorter than a second based on time information having an accuracy shorter than a second.

With respect to a timepiece capable of running on a battery and a device having a clock generator with cycles shorter than those of the timepiece, a method is provided for synchronizing the timepiece with time information having digits of shorter than a second. This method comprises a step for adding a first time period corresponding to the characteristic of the timepiece to a time period obtained from the time information, a step for dividing information on time to which the time period is added between information on time of a second or longer and information on time shorter than a second, a step for adding cycle time to the information on time shorter than a second for each of the cycle times of the clock generator, and a step for determining whether the information on time shorter than a second has been carried to that of a second or longer. Based on a determination result by the determination step, a second time period corresponding to the characteristic of the timepiece is added to the information on time of second or longer, and what is thus obtained is set on the timepiece.