Quick facts

• A moonphase complication tracks the phase (new, full, half or quarter ) of the moon. The phases of the moon are shown on a rotating disc through a half-circle/ • “bosom” aperture or on a radial aperture which uses a conventional hand. The exact length of the lunar cycle (29 days, 12 hours, 44 minutes and 3 seconds) creates a challenge in terms of accuracy. Common moonphase displays use a 59-tooth driving wheel and needs to be adjusted every 2.5 years; refined ones with a 135-tooth wheel can stay accurate for more than 120 years.