Seiko Premier Perpetual Calendar Quartz SNQ159 SNQ159P1 SNQ159P 100M Mens WatchSeiko Premier Perpetual Calendar Quartz SNQ159 SNQ159P1 SNQ159P 100M Men's Watch Amazing engineering worth your every penny! Youll only have to re set the calendar if the battery has completely died. The watch, however; stores enough power to keep working for the time youd usually take to remove and replace the battery if you keep a spare one handy. You'll never have to set the perpetual calendar again if you dont allow the battery to die out