The Ultimate Guide to 3 Types of Watch Calendars

A calendar is a universal system of organising days to mark the passage of time.

The watch calendar complication on a luxury watch defines the height of luxury watch making. Its mystical ability to tell the correct date is no simple science. These complications solves the complexities in the calendar, such as different days in the months of the year and the correction for the leap year. The different categories of watch calendars, namely complete calendar, annual calendar and perpetual calendar are complex within their own mechanism. But before we divulge into the workings of these watch complications, let’s first learn about the basics of time keeping, beginning first with the knowledge of a calendar.

History of Calendar

A calendar is a universal system of organising days to mark the passage of time. The time period or units of time have been defined as seconds, minutes, hours, days, weeks, months and years. A date is defined as the singular entity of a passage of time for the period names as a day. Over centuries, the movement of the sun and moon have been defined as the most naturally occurring regular event. And thus, logically, forms the basis of measurement of time for all possible sciences related to timekeeping.

Gregorian calendar is the current standard across the world

Initially the roman calendar was based on the lunar cycles and thus had only 10 months. Later, when Roman astronomers had proposed a more accurate calendar based on the solar cycle, they added two months to the original ten month calendar.

The calendar was given lot of reforms by Julias Caesar. With many other advancements over a long period of time, the Gregorian calendar became the international standard. Nowadays, it is used by pretty much everyone in the world. It is purely a calendar based on the movement of the sun with a cycle of leap days in a four hundred year cycle. Thus each Gregorian year has either 365 or 366 days, depending on the insertion of 29 February to accommodate a leap year.

Invention of Watch Calendar Mechanism

If you researching the formation of calendar, it would be a long and complicated study and would need a lot of time. It actually is a very complicated process. It must not have been easy to invent a watch calendar mechanism to show all of these complications via gears and tooth. The watchmakers defined a mechanism via which they distinguished the thirty days months from the thirty one days months. They also looked at twenty eight days in February, which further needs a change every four years.

The horologists of that era, took the challenge and invented undoubtedly the finest working machinery. Something of this sort is something that a common man can’t achieve. It is surely a work of genius. The whole mechanism is controlled via hundreds and hundreds of gears.

This complicated feature, is right termed as a ‘watch complication’. It appears only on the high end watches. Based on the complexity, the mechanism is divided into three categories: Complete calendar, Annual calendar and Perpetual calendar. Lets look at the working mechanism behind each of them.

Complete Calendar Watch

The entry watch with the watch calendar complication is complete calendar watch. It has an ability to show day of the week, date and month of the year. Most often, the complete calendar watches also show the moon phases. This moon phase feature is not directly related to the working of a complete calendar watch.

In a calendar watch, you need to advance the date for the months with less than 31 days. Thus in a year, it needs to be reset five times manually. The dates that it need to be reset on are Mar 1, May 1, July 1, Oct 1 and Dec 1.

Annual Calendar Watch

A step up from the complete calendar watch is something that is called as annual calendar. The annual calendar watch mechanism can easily distinguish between complexity of the thirty one day month vs the thirty day months. It, however, fails to correct the twenty eight or twenty nine days in February. Thus the only time that the watch needs to be reset is on Mar 1. If the watch is not reset on the last day of February, the mechanism thinks of the February month as 30 days.

This type of watch calendar technology was initially patented by Patek Philippe in 1996 and has been under continuous improvisation since. Luckily this mechanism has now been used by the finest of watch makers across the world. The introduction of the annual calendar made luxury watches more affordable. Annual calendar is now being available as an alternative to the perpetual calendar.

Antoni Patek
Jean Adrien Philippe


Perpetual Calendar Watch

The crème de la crème of the watch calendar complication is called as perpetual calendar. It is found only in the finest and most luxurious ( and pricier ) watches. The perpetual calendar watch shows basics like day of the week, month of the year and the date along with the moon phase in some watches. In some of the high end perpetual calendar watch, it also shows its position in the four year leap year cycle.

The mechanism on the perpetual calendar watch has been made in such a way that it would need to be adjusted only once in a 100 year time. If you do buy a perpetual calendar watch now, it won’t need a reset until February 28 2100. If you do buy it, you can actually leave a note for your great grandson to reset the watch on Mar 1 2100. Isn’t that cool and something that is unbelievable yet believable at the same time.


Perpetual calendar and moonphase wristwatch. Photo by Rama Image Source