What is the primary function of a moon phase watch?

The primary function of a moon phase watch is to indicate the current phase of the moon. These watches feature a display that visually represents the moon’s cycle, allowing the wearer to see whether the moon is new, waxing, full, or waning. This function is based on the lunar cycle, which lasts approximately 29.5 days, and it provides an elegant way to track the changes in the moon's appearance over time.

Moon phase complications are appreciated not only for their functionality but also for their aesthetic appeal, often enhancing the overall design of the watch. Understanding the lunar phases can be useful for activities that are influenced by the moon, such as fishing, gardening, and even certain cultural or religious events.