Let’s be honest: a moon phase indicator on a watch adds great visual interest to a watch dial. It’s also a testament to a brand’s superb watchmaking craftsmanship, and it’s fun to see the moon as it moves (albeit very slowly) through its cycle. But in 2023, do we really need a moon phase indicator on our watches? Not so much anymore, but in the early days of watchmaking, a moon phase was an important tool.
Moon Phase: Watchmaking Craftmanship in Circles of 29.5 Days
A moon phase complication, as its name suggests, displays the phases of the moon. The moon is seen through an aperture on the watch’s dial. Generally, the moon phase aperture is semicircular in shape, creating a window through which the moon can be seen. Beneath the aperture, a slowly rotating disc depicting the current phase of the moon travels at the rate of a full moon cycle, which is 29.5 days in length.
During the 29.5 days, the moon phase complication depicts the current phase of the moon as it waxes and wanes. A new moon, which is the start of a moon phase, occurs when the earth completely blocks the sun’s light from the moon, rendering it invisible. As time progresses through its monthly orbit, the visible portion of the moon becomes larger. The waxing phase transitions to the first quarter phase, when the right side of the moon is visible. The next phase is the full moon, afterwards comes the third quarter, and finally the moon wanes, eventually disappearing again at the new moon.
Moon Phase: the mother of invention?
How did the moon phase complication come about? Necessity is the mother of invention, as the saying goes. When moon phases were first invented, they provided essential information for several purposes. The moon’s greatest impacts on life are the time, tides, and light.
For navigation at sea, the moon was an indicator of the direction of travel and its phases helped indicate the passage of time. Tides are affected by the phases of the moon as well: high tide is at its highest during a full moon.
For the military, soldiers knew that it would be easier to travel at night with the light of the full moon. Rendezvous could be scheduled based on the phase of the moon. Hunting nocturnal animals is easier by the light of the moon.
It’s 2023: Do we still need moon phase watches?
Today, we don’t need a moon phase as a tool. Modern electronics tell us everything we need to know for navigation and military purposes. Yet, the moon phase remains a very popular and desirable complication in both men’s and women’s watches.
Take, for example, the Jaeger-LeCoultre Reverso. Moon phases are plentiful in the collection. In addition to beauty, there’s a certain refinement they impart.
Many of IWC’s Portofino and DaVinci watches also feature a moon phase. While the brand is known for its spare design aesthetic, the moon phase timepieces remain a very popular choice.