Moon-Phase Watches: How They Work and How to Set Them
Moon-phase watches translate the lunar cycle—about 29 days, 12 hours, and 44 minutes—into a mechanical display. Traditional models use a 59-tooth wheel and two moon images, advancing the disk once per day; this simple design loses about eight hours annually and needs correction roughly every three years. More complex mechanisms can be far more precise, while some watches display both hemispheres or multiple stages of the lunar cycle. To set a moon-phase display, follow the watch’s instructions and avoid adjusting it during periods when the calendar mechanism is engaged. For a separate pusher, advance the display to a full moon and press once for each day since the most recent full moon. For crown adjustment, set the display to the last full moon’s date, then advance the calendar to the current date.
Buying Time Analysis: This story explains how moon-phase watches translate the lunar cycle into mechanical displays, compares their precision, and helps owners set them correctly.
