Perpetual Calendar

A perpetual calendar watch is a specific type of timepiece displaying calendar indications, but which also does complex calculations based on a series of mechanical gears. A perpetual calendar is capable of displaying the right date, whatever the length of the month (28, 30 or 31 days) but also automatically takes into account leap years, when February counts 29 days. As such, a perpetual calendar only requires one correction every 100 years – when a so-called secular year occurs.