A year indicator is a complication that shows where the current year falls in the four-year leap cycle. It is used on perpetual calendars. These add a 29th day to February every fourth year without needing to be reset. The indicator shows the wearer which year of the cycle the calendar has reached.
How does a year indicator work?
The indicator follows a cycle of four years. Three are ordinary years, and the fourth is a leap year, when February gains a 29th day. Patek Philippe dials mark the leap year with a 4, in either Roman or Arabic numerals. The display does not have to sit on the dial. H. Moser & Cie. places it on the movement side of its perpetual calendar, so it can only be seen by turning the watch over. Watches from Jaeger-LeCoultre and Girard-Perregaux also have this indication.
Where it comes from
The indication first appeared in pocket watches. Revolution credits Audemars Piguet as the first maker to put it on a wristwatch. The brand’s first series of perpetual calendar wristwatches with this indication came out in 1955. On these early reference 5516 watches, a subdial at 6 o’clock counted through 48 months, which makes four years. The first pieces spelled out every month on that subdial. Later pieces dropped the month names for a simpler layout. Phillips states that no other brand offered a perpetual calendar with a leap-year indicator until 1981, when Patek Philippe introduced the reference 3450.
Not to be confused with
An annual calendar does not track the four-year leap cycle. As a result, it has to be corrected by hand every fourth year. This is the main difference between an annual calendar and a perpetual calendar. A perpetual calendar handles the leap year on its own, with no correction by hand, and the year indicator shows where the current year falls in that cycle.
Does it handle century years?
The plain four-year cycle breaks at century years. A year ending in 00 is a leap year only if it divides evenly by 400. Any other century year has no 29 February, even though it would otherwise fall fourth in the cycle. The year indicator follows the plain four-year cycle, so this exception sits outside what it shows.
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