What a moonphase does
A moon disc rotates through a 29.5-day synodic cycle and shows the current phase through a circular aperture. It is a decorative and mechanical pleasure rather than a practical function.
How to set it
- Check that the watch is outside the restricted setting window, typically 21:00 to 03:00.
- Press the recessed pusher at 4 or 8 o'clock with a stylus until the aperture shows a full moon.
- Count forward from the lunar date — for the eighth day of the lunar month, press seven times.
Buying advice
Moonphase is often combined with complete or perpetual calendars, which adds complexity and cost. A single moonphase model is easier to live with day to day.