About the Annual Calendar
The annual calendar is a mechanism patented by Patek Philippe in 1996 that can automatically determine which months end on the 30th and 31st.
Traditional, simple calendar types that only display the date required manual date adjustments for months that did not end with 31 days, but annual calendars are complex features that eliminate the need for such manual adjustments, making them highly practical.
Since the last day of February is not recognized, the date needs to be adjusted only once a year, on March 1st.
Perpetual calendars require adjustments if they are stopped and not used for many years, as you need to check if that year is a leap year. Also, while many of the highest quality models are extremely expensive, annual calendars simplify the system and make complex functions more practical.
