On Leap Day 2012 - A great day for the perpetual calendar!

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On Leap Day 2012 - A great day for the perpetual calendar!

Post by andrema on Wed 29 Feb 2012, 1:53 pm

February is an intersting day for those of us who fancy complicated watches. The question of "How exactly does the watch know when to include the extra day in February?". Well, I wanted to provide a little insight as well as share a quick write-up that Hodinkee did on the PP 2497 Perpetual Calendar watch...


So, what is a perpetual calendar watch?

Well, here is a great explanation from TZ:

5.3 What's a Perpetual Calendar? How is it different from an Annual Calendar or Triple-Date?

A perpetual calendar is the most developed form of the simple date window on a typical watch. It keeps track of date, day-of-the-week, (sometimes weeks), months, year, leap years, and sometimes even centuries. Because of the relatively complex rules governing the Gregorian calendar, including the varying lengths of months, and leap years every four years, a typical perpetual calendar has wheels turning from several times per second (e.g. balance wheel) all the way to once every four years. Because of the complexity of the Gregorian calendar, some perpetual calendars will require an experienced watchmaker open the watch to make an adjustment at AD 2100, or later (assuming that an experienced watchmaker still exists then). Some less complex calendars are also available:

  • Semi-perpetual calendars (e.g. the Breitling Montbrilliant 1461), which requires an adjustment on leap year day only.

  • annual calendars (of which the Patek Philippe 5035 is an outstanding example), which only require a user adjustment once every February
  • "triple date" calendars, which contain month, day, and date - but need to be manually advanced at the end of each (short) month

Some would say that the inconvenience in resetting the date on a true perpetual calendar is the main reason for the existence of the watch winder.


This is an interesting read from Hodinkee that highlighs a finely crafted example of a perpetual calendar watch: The Patek Philippe 2497

The Patek Philippe 2497: On Leap Day 2012, We Show You A Perpetual Calendar You Need To Know

You won't find the owner of a perpetual calendar any happier than you will today, February 29th. You see, one of the coolest things about a true perpetual calendar is that it automatically knows and adjusts for leap years. Thing is, they don't come around too often, so every February 29th, people that are lucky enough to own a perpetual calendar go a little nutty and start showing complete strangers their watches on the streets.

So, on this leap day, we though we'd show you a famous perpetual calendar that you should know about. It is, of course, from Patek Philippe, and its reference is the 2497. It is a traditional manually wound perpetual calendar and it was launched in 1951.

The 2497 was introduced alongside the 2438-1, which was the same watch with a waterproof case and though it was produced for over ten years, only 179 examples were made in total, of both references. The 2497 is traditionally divided into two series, differentiated by their dials. Series one is as above on Ben's wrist with alternating dots and arabic numerals and feuille hands, while series two is as seen here[/color][/u][/url] with all applied hash markers and dauphine hands. Estimates on 2497s are anywhere from $220,000-$350,000 these days, with the last one selling publicly for $314,500 in December of 2011 in NYC[/url]. So, next time leap day comes around and your annoying friend with the perpetual calendar shows you his watch, tell him "if it's not a Patek 2497, i'm not interested".

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Re: On Leap Day 2012 - A great day for the perpetual calendar!

Post by Tickety on Fri 17 Aug 2012, 1:21 pm

andrema wrote:Estimates on 2497s are anywhere from $220,000-$350,000 these days, with the last one selling publicly [u]for $314,500 in December of 2011....

too bad I already spent my watch budget this month or I'd be all over one of these tongue

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