Celebrating the Leap Year with Perpetual Calendars
Celebrating the Leap Year with Perpetual Calendars.
- By Jon Zhang of JZ&F
I always have a special, warm and fuzzy place in my heart reserved for the last day of February…
Why is that?
Watches with simple calendar date wheels (e.g. your typical Rolex) have calendars that go to the 31st for every month, and require the owners to pull out the crown and manually adjust the date setting at the end of every month that has less than 31 days.
A notch above that is an annual calendar complication which can distinguish months with 30 days and 31st days, and requires an adjustment at the end of every February, when annual calendar would deficiently categorize it as a month with 30 days.
Sitting on the top of this date complication hierarchy is the perpetual calendar movement, which, with a set of additional gears, knows that February has 28 days. Not only that, a true perpetual calendar would have a leap year indicator and can figure out that every 4 years, the leap year February has 29 days. Assuming that the watch is kept running all the time, the date display on the perpetual calendar would only need to be set manually every 100 years. Oh! Joy!!
(However, years that are evenly divisible by 100, but not by 400, do not contain a leap day; thus 1900 did not contain a leap day while 2000 did, and 2100 will not contain a leap year... something to keep in mind when your beloved perpetual is passed down to you great-great-great-grandson).
Hence, around midnight of February 29, while most layman watches would point to the imaginary February 30th, perpetual calendars would proudly jump to arch 1st. This is a day that pays homage to perpetual calendars, high complication mechanical watches, and human ingenuity with regard to micromechanics. This is the day for purists who appreciate these things.
What better excuse to celebrate! Traditionally, on this day, when I was living in New York, I would partake in a get-together with a group of like-minded watch aficionados, have a smashing time, and in our collective drunken stupor "watch" the date hand jump to March 1st!
I’ve had the great honor to organize such a get-together this year. It is our lovely Emerald City's first perpetual event.
A few of us got together for dinner, the table has an impressive set of 10 rare perpetual calendars – rivaling that of the best combined inventory of Seattle’s local watch stores!
Lively watch-related discussions ensued during dinner. Curiosities were piqued...
After dinner, we set our perpetuals a few hours ahead, to observe the jump to March 1st.
On the last day of February, most perpetual calendar would gradually shift the date starting from 10:30pm, and finish the transition to March 1st around 1am.
To illustrate, at 11:30pm, both the IWC and Franc Vila have the date displaying Feb 31st...
By a little bit after midnight, both watches successfully moved to March 1st
Hope you have enjoyed this blog post, and Happy March!