An annual calendar is a mechanism with which the date of a watch needs to be set only once a year (depending on leap year at the end of February). In contrast to this, watches with perpetual calendar are able to display leap years properly without manual intervention.
Depending on the display used, this complication may also be called a full calendar, complete calendar, or triple calendar These display the day, date, and month.
The annual calendar complication did not arrive on the market until 1996 when Patek Philippe introduced the Ref. 5035. It remains a rare complication to this day, with most watches featuring a simple calendar.
In recent years, manufacturers have disguised the calendar complications to greater extent. The 2006 H. Moser & Cie. Perpetual 1 uses a small arrow-shaped pointer at the center of the dial to indicate the month using the hour markers. The Rolex Sky-Dweller, introduced in 2012, uses a colored marker outside the hour markers to indicate the month. Both of these leave just a standard date window as their only obvious calendar component.