Provided is a radio-wave wristwatch that receives radio waves including day-related information from a satellite in a global positioning system, wherein the number of revolutions of the day-related information is accurately updated even when there is a decrease in a power supply voltage. A radio-wave wristwatch (1) according to the present invention comprises: reception means (11) for receiving radio waves from a satellite and extracting day-related information; timer-circuit halting means for halting the operation of a timer circuit in response to a power supply voltage; timer-circuit halt detection means for detecting that the timer-circuit halting means has halted the operation of the timer circuit (13); a nonvolatile memory (23) for storing the day-related information and the number of revolutions of the day-related information; and revolution number updating means for, when the timer-circuit halt detection means has detected that the operation of the timer circuit has been halted, updating the number of revolutions of the day-related information in accordance with the result of comparing the day-related information extracted by the reception means (11) and the day-related information stored in the nonvolatile memory (23).
