What is a Perpetual Calendar?

perpetual calendar 2A perpetual calendar is a type of watch complication, which calibrates and displays the date, and how many days there are in each month, taking into account any unusual factors such as leap years. Most perpetual calendars have been designed to display the date, month, day of the week, and year for the next 50+ years. Perpetual calendars can only be crafted by very highly skilled watchmakers, and so are usually only found on very high end and expensive watches.