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Watch GlossaryPerpetual Calendar

A perpetual calendar complication not only knows the number of days in each month, it also knows the year so that it will automatically adjust for leap year

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What is a perpetual calendar?

A perpetual calendar is a complication in a watch which displays day of the week, date and month for decades without having to make any adjustments. Perpetual calendars are even adjusted to show 29 days in February during a leap year. Some perpetual calendars can effectively show the day and date for up to a century.

Perpetual Calendar Watches
The Schaffausen-based brand’s perpetual calendar makes an appearance in practically all their collections, and especially in the Portugieser—one of the brand’s more popular lines

The first wristwatch with a perpetual calendar was introduced in 1925 by Patek Philippe. The movement that powered the watch, which included a perpetual calendar complication, was initially developed for a pendant watch and simply placed in a wristwatch case. In that respect, the first wristwatch powered by a movement with a perpetual calendar complication was the Breguet No. 4244. It was the first wristwatch to feature a perpetual calendar that had been developed specifically for it. The Breguet wristwatch was manufactured in 1929 and sold for an extremely high price, owing to the sophisticated complication of the perpetual calendar.

The Watch Guide

Another rendition of H. Moser’s award-winning perpetual calendar, this one here is in a Streamliner timepiece, from the brand’s collection of sport watches with integrated bracelets

The Watch Guide

This H. Moser & Cie. Streamliner Perpetual Calendar model has a leap year indicator on the reverse, seen on the manual-winding HMC 812 calibre, through the exhibition caseback

How does a perpetual calendar function work?

A perpetual calendar operates on a simple principle. It consists of 14 one-year calendars including seven calendars for each day of the week for a non-leap year and seven calendars for each day of the week for a leap year. In addition to these calendars, there has to be a system which will decide which one-year calendar to be used for any given year.

Perpetual Calendar Watches
The Bovet Dimier Récital 21 displays the day at 12 o’clock, the month at six, and leap year indicated at three o’clock. Surrounding the main timekeeping is a retrograde date display, whose mechanism slows down the indicator when the retrograde jump takes place from the end of the month back to the position of the 1st for the following month

Alternatively, a perpetual calendar can consist of 28 one-month calendars including seven calendars for each day of the week for 28, 29, 30 and 31 day months. In addition to these, there has to be a system that will keep track of the month and the year and decide which one-month calendar needs to be used for a given month. Perpetual calendars are rather complex in their mechanism and thus usually incorporated in watches manufactured by master watchmakers.

The Watch Guide

‘Perpetual’ implies forever, and that’s how long a perpetual calendar watch is supposed to tell the correct date without adjustment

The Watch Guide

Some perpetual calendars even display the year and moon phase. This adds to the complexity of the movement, thus making it more sophisticated and usually more expensive

While most perpetual calendars display day of the week, date and month, some even display the year and moon phase. Although moon phase is a separate complication seen individually in watches, many perpetual calendars incorporate this functionality in their system. This adds to the complexity of the movement, thus making it more sophisticated and usually more expensive. Such perpetual calendar movements require a high degree of skill in their making. Usually, only master watchmakers who have excelled in their field will attempt to work on a perpetual calendar movement, especially one that is more sophisticated and complex in its functionality.

Perpetual Calendar Watches
Watchmakers have mastered the art of creating perpetual calendar watches to the extent that they automatically consider the differing number of days in a month, including leap years. Perpetual calendar watches typically indicate all important calendar details—the date, the day, the month, and the year

Perpetual calendars are incorporated in the timepieces of Swiss watchmakers like Breguet, IWC, Jaeger-LeCoultre, H. Moser & Cie., Bovet, Carl F. Bucherer, and Frederique Constant among others.

Also read: Top 10 Perpetual Calendar Watches

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