The watch only syncs time but doesn’t set the calendar for you when you go aboard or after return. You need to set the calendar by yourself.Slightly pull out the middle crown to its first click position and then turn the crown to set the calendar and pushes it back after it’s set.If you accidentally pull out the crown too hard to its second click position so that the hands are being adjusted instead of the calendar or if the calendar advances during the middle of the day instead of midnight (after your calendar setting), then you need to reset the calendar and all the watch hands.Please follow the below video to reset watch hands and calendar of your watch.https://youtu.be/XMlKYk7c_rM