Days of the Year
An in-depth look At the one horologicAl complicAtion we use the most And its extended fAmily
Among the many mechanical complications in a watch, the most common and useful one—and perhaps also the most underappreciated variety—are calendars. In the realm of fine watchmaking, however, calendar complications encompass much, much more than simple day/date displays. In fact, you’ve likely heard of terms like “perpetual calendar,” “annual calendars” and so on. So, below, we will take you on a brief tour of the complication family bringing the days of the year to your wrist.
At the lowest tier of the calendar complication family we have the simple date window. Following this is the day-date indicator with two apertures, one for the name of the day and the date. It should be noted, however, that these basic mechanisms do not take the month into account. In other words, these watches always operate on a 31-day cycle, forcing the owner to manually adjust the dates at the end of every 30-day month as well as at the end of February.
Another step up and we have the complete calendar, sometimes also called the triple calendar simply because it indicates three bits of information: day, date and month. Still, this category of watches still doesn’t take differing month lengths into account, and manual adjustment will be necessary at the end of certain months.
Of course, slight variations of presentation based on these basic concepts also exist. Some watches, for instance, emphasize the date display by using large, double apertures with the left window displaying 0 to 3 and the right 0 to 9. Others use a small sub-dial to indicate the date of the month or an extra hand that points to dates placed along the outside periphery of the dial. The latter is sometimes known as a “Bankers” date display.
From here on, things get much more complicated, but also much more fascinating. So, stepping up from the complete calendar we have the annual calendar. Put simply, an annual calendar “knows” which months end on the 30th and which ones run until the 31st. The problem, however, is February. You can blame the Ancient Romans for the mess with February, but what this means for us today is that if you have a watch with an annual calendar complication, you still have to manually adjust the date display at the end of every February.
Fortunately, the next tier of calendar complications knows how to deal with the pesky second month. We are, of course, talking about perpetual calendars. Also known as the the perpetual calendar is actually considered grand complication due to its sheer complexity. As the name implies, a perpetual calendar can track the correct date perpetually. Well, at least until 2100 that is.
Here we come face to face with yet another quirk of the Gregorian calendar— one that is perhaps a bit lesser known. See, we are all familiar with leap years, right? Every four years, we add an extra day to February. The thing is, not every year divisible by four counts as a leap year: If a year is divisible by 100 but by 400, then it’s counted as a normal year. So, 2000 was a leap year, but 2100 won’t be. For this added complexity, you can thank Pope Gregory XIII—although he did so in an attempt to fix the mess left by the Romans, so he’s not entirely to blame, we guess.
Back to the perpetual calendar, the basic mechanism of this complication has a “mechanical memory” of 1,461 days, or four years including one February 29th. Left on its own, a perpetual calendar watch will essentially show the correct date for the foreseeable future. Sure, it will need