The phases of the moon are actually lunar calendars, indicating the cycle of the moon's waxing and waning. The sun, moon and stars are the most intuitive celestial bodies, but the phases of the moon are related to latitude. 

 The moon phase function is often placed in a special-shaped semi-circular window, which includes a semi-circular arc and two small circular arcs. This elaborate shape, combined with the moon on the moon phase disc, tells us more accurately what the moon looks like at the beginning or end of a cycle. 

 The moon phase is based on a 29.5 day cycle to show the state of the moon on the moon phase disc. There are two moons on this moon phase disc, and there are 59 teeth on the edge. After being pushed by the transmission wheel, the moon phase wheel moves forward by one tooth every day. At this time, the change of the moon phase profit and loss can be displayed on the dial in time. The 59-tooth moon phase wheel comes from the average value of the moon phase profit and loss every 29.5 days. Since the moon's precise rotation period is 28 days, 12 hours, 44 minutes, 2.9 seconds, every roughly 33 months, the moon's phases are displayed with an error of 24 hours. There is usually a moon phase adjustment button on the case, and the moon phase display is relatively independent from functions such as chronograph and perpetual calendar.