How to set a moonphase watch
Centre the full moon, then press the corrector once for each day since the last full moon. A step-by-step guide with the safety rules.
How the display works
Most moonphase watches use a disc with two moons on it, advanced one step a day. The disc has 59 teeth for two lunar cycles of about 29.5 days each, so it drifts by about one day every two years and eight months. High-precision displays use different gearing and drift far less.
Steps
- Find the corrector: a recessed pusher on the case side, or a crown position. Use the supplied tool or a wooden toothpick, never a metal pin.
- Press until a full moon is exactly centred in the window.
- Press once more for each day since the last full moon. The moonphase tool on this site shows that number.
Rules
- Avoid the corrector between about 9pm and 4am on the watch, when the disc may be moving.
- If the watch also has a date, set the time and date first, then the moon.
- Recheck against the real moon every year or two.