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Watches - Watch Anatomy

What is a Perpetual Calendar?

Unless you’re a watch enthusiast, chances are you’re going to find the many names for a watch’s date function—date, day-date, annual calendar, or perpetual calendar—unnecessarily confusing. Well, the perpetual calendar is the most impressive of these and in fact it’s arguably the pinnacle of watch complications. It’s functional, unfathomably intricate, good-looking and, of course, very expensive. But what is it, how does it work, and which are the best examples?

A PC takes into account the different lengths of the months, even on leap years. So, providing it’s kept wound and undamaged, it only needs to be set once per few hundred years, or whenever our calendar skips a leap year (March  1st, year 2100, is the next time this is set to occur).

Making this work involves squeezing a couple of hundred parts into a confined space about the size of two two-pound coins, one sitting on top of the other, and programming these parts for 1,461 days (equivalent to four years). This, of course, is rather tricky, which is why it’s only attempted by the world’s greatest watchmakers.

iwc portuguese perpetual calendar

Where did it all begin?

Many of the most sought-after watches at important watch auctions are perpetual calendars, and more often than not they’re made by the long-time undisputed champion, Patek Philippe. Until 2011, the first perpetual calendar wristwatch was thought to be a Patek Philippe piece sold in 1925. But the movement had originally been made for a pendant watch. Then, at a Christie’s auction, a watch popped up for sale that surprised watch industry experts and even officials at the brand it supposedly came from. The watch was a Breguet Retrograde Perpetual Calendar dated 1929. Not only was this now potentially the first PC specifically made for a wristwatch, but it wasn’t a Patek.

When these watches first hit the scene in the twenties and thirties they were the forefront of technology and were very useful. They sparked a perpetual calendar craze but they were so difficult to make that they were only available to the super rich.

patek philippe retrograde perpetual calendar

The Different Calendars

Date

In 1945, Rolex came up with the first watch with an automatically changing date, the Rolex Datejust. It was a date function at a tenth of the price of the PC, but these watches, as with most date watches today, are set to run for 31 days. This means they need to be adjusted at the end of any month that doesn’t have the standard number of days. Today, with our access to technology, the idea of adjusting the date seems ludicrous, but this date concept is still the most widespread.

Day-Date

Rolex followed up the date function with the Rolex Day-Date, which spells out the day of the week as well as giving the date. These watches were very popular but they also require adjusting at the end of any non-standard month.

Annual Calendar

The annual calendar only needs adjustment once every four years as it doesn’t account for leap years. It's more accessible than the perpetual calendar and much less common.

Perpetual Calendar

The PC shows the day, date, month and takes leap years into consideration. The classic layout involves at least three subdials and often a moon phase indicator.

The Best Perpetual Calendars Today

Many of the top watchmakers today offer a perpetual calendar, but making it is still as challenging as it ever was and the number of man-hours that go into it hasn’t changed. The original designs are still being tweaked and reimagined, and today the perpetual calendar comes in a number of shapes and sizes.

The Best Value

Due to the level of expertise required, perpetual calendars are very expensive, usually upwards of £35,000. It has only really been in the last decade that brands have been able to offer slightly more affordable versions. Montblanc and Frédérique Constant now have models under £10,000. Further savings can be made when looking into the pre-owned market. This IWC Portuguese in 18k rose gold is an exceptional example of a perpetual calendar and is now discontinued, but can be bought pre-owned for around 50% of it's RRP.  

iwc portuguese perpetual calendar

The Retrograde

In watchmaking "retrograde" refers to the way information is presented, more specifically, a numbered track and pointer that replaces a sub-dial. One of the most recent (2011) model Patek Philippe Perpetual Calendars is a Retrograde, which features a central ark with a date track and a small arrow that reverts back to one at the end of the month.

patek philippe retrograde perpetual calendar

The Most Advanced

Possibly the most exceptional perpetual calendar was released at SalonQP 2015. It was the result of a collaboration between maverick watchmakers MB&F and the talented Northern Irish watchmaker, Stephen McDonnel. The Legacy Machine Perpetual was made of 581 parts, many of which appear to float inside a domed watch case. His PC was programmable at the push of a button, or four buttons, which meant it was easily adjustable in the event of it not being wound or going in for service.

mb&f legacy machine perpetual LMP salon qp

 

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