Patek Philippe introduced the first wristwatch with a perpetual calendar in 1925.
A perpetual calendar is a mechanical calendar complication designed to account for months of different lengths and the leap-year cycle. When correctly set and kept running, it can display the correct calendar date without manual adjustment through most of the Gregorian calendar cycle.
Patek Philippe made the first known perpetual-calendar wristwatch in 1925. The watch was based on a movement originally associated with a women’s pendant watch and was later fitted into a wristwatch case for the company’s production history.
A perpetual calendar is not the same as an annual calendar. An annual calendar usually needs correction once a year at the end of February, while a perpetual calendar is designed to handle February’s changing length, including leap years.