Beginners Guide: Astronomical Complications

Since ancient times, humanity has looked to the stars to help keep track of the time, days, and the seasons. And though the technology has since evolved, modern time-keeping is still based on the movement of the Sun and the stars. In this article we will introduce timepieces that execute these astronomical complications beautifully.

Date Display

What is often regarded one of the simplest complications is also one of the most useful. Date windows are so commonplace that they're often overlooked or taken for granted. Usually the date window is placed at the 3 o'clock position, but there are signature time pieces that also break the mold in very creative ways. Simple day-date displays do not take into account the different lengths in each month, and therefore need to be manually corrected at the end of every month.

Day-Date Display

The day-date display takes it up a notch in terms of functionality, showing the day of the week as well as the date. The day-date is commonly placed side-by-side at the 3 o'clock position, but you can also find the day-date at the 12 o'clock position in some more classically designed watches.

Annual Calendar

The annual calendar is a more complex version of the day-date display, with an additional indication that shows the month of the year. The annual calendar automatically adjusts to months that are 30 or 31 days, but needs to be adjusted once a year in March, to account for the month of February, which only has 28 days.

Perpetual Calendar

While the annual calendar needs to be set once a year, the perpetual calendar does not. The perpetual calendar automatically changes to the correct date, even in the month of February.

Equation of Time

An equation of time complication shows the difference between solar time and man-made time. True solar time and the length of the day varies as the earth orbits around the sun on its axis. Mean time ignores these variations to create equal hours and equal days. The equation of time complication will usually appear on the dial face indicating the difference between mean and solar time.

Moon Phase

The moon phase is often considered more of an aesthetic complication rather than a practical one. However, the moon phase remains popular due to the fact that it's one of the most romantic complications a watch can have. The moon phase display shows the waxing and waning of the moon based on the lunar cycle, which takes place over a period of 29.5 days.