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A Brief Explanation about a Major Complication: the Perpetual Calendar

Le 24 September 2015

Perpetual calendar, complete calendar, single or instantaneous calendar,physical quantum and “Quantum of Solace” (a James Bond film which, apart from the presence of Olga Kurylenko as the Bond girl, can be summed up as a not overly successful pun). Are you a bit lost? You recognize the names of these complications but have never understood how they differ or their technical details? Don’t panic. All will be revealed.

Jaeger-LeCoultre - Perpetual Calendat Pink Gold (Wrist)

To continue our plan and fulfil our desire to make fine watch-making even more available, accessible and comprehensible, we will begin with the first episode of a series devoted to timepiece complications, which I hope, as you read on, will be complicated for you in name only.

We’ll discuss all of that without big technical words (where possible but sometimes, we have to call a spade a spade)and in a relaxed manner.

So, let’s get going! No need to worry – it’ll be OK. Today, we are going to assess a perpetual calendar, QP for enthusiasts, and what better illustration than the Jaeger-LeCoultre Master Ultra Thin Perpetual, reference 130 35 20.This is one of the most sober expressions of the perpetual calendar in a 39-mm case, just 9.2mm thick. Why? Because it’s really very beautiful, because we like it and because it might look less impressive to you compared to many other watches.

Jaeger-LeCoultre - Perpetual Calendar

So what’s this Perpetual Calendar all about?

Let’s move on and discover the myth behind all of this. First and foremost, what is a Calendar? and what does the term Perpetual actually mean?

It’s extremely simple – you’ll see:

In watchmaking, the calendar simply means the display of the date by the day of the month.

Therefore, from 01 to 31, depending on the month, this indication is mainly displayed in the guise of a rotary disk or a hand, and is very much in vogue (simple calendar: the date is displayed according to the day of the month and is adjusted manually by the wearer.)

A Perpetual Calendar is therefore a watchmaking complication, which constantly displays the calendar (the date) (in a perpetual manner) (without intervention).

All of this happens mechanically, with no human intervention, bearing in mind irregular months and bissextile years.

Since the days, months and years are needed in order to display this perpetual calendar, these also often appear on the dial. However, they don’t have to be displayed for a calendar to be perpetual.

Jaeger-LeCoultre - Perpetual Calendar White Gold

Shall we go into a bit more detail?

The instantaneous calendar:

Having the same function as a single calendar (displaying the date and adjusted by the wearer),a calendar is said to be instantaneous when the mechanism allows a very rapid change at midnight, not gradually as is the case with most automatic movements (generally between 23:00 and 02:00).

The complete calendar:

A calendar is said to be complete when the mechanism can display all of the calendar information on the dial: the calendar (date: 1-31), day (Mon-Sun), the month, year and lunar phase. However, without perpetual characteristics, these watches require frequent human intervention, ideally on a monthly basis, to stay up to date. These adjustments can be made using correctors, often located on the side of the case. (Discover a complete Montblanc calendar here we talked about it recently.)

Youve guessed it this beautiful Jaeger-LeCoultre is, therefore, technically a Complete Perpetual Calendar. You have to know that it is not instantaneous but progressive, like many other Perpetual Calendars.


Let’s put things in order – a single, instantaneous, complete and perpetual calendar. Now you know the difference and can, in turn, explain it simply and concisely, can’t you? Well done!

So, it’s high time to spread the good news.

Start off with your son or young brother. Its never too early to lay solid, healthy foundations. Otherwise, some complete and utter stranger will do it. Your son or brother will thank you for it in the long run!