Does a perpetual calendar ever need correcting?

Only in 2100, which isn't a leap year under the Gregorian calendar, and of course whenever the watch stops.

What's the difference between a perpetual and an annual calendar?

An annual calendar knows 30- and 31-day months but not February, so it needs one correction a year on March 1. A perpetual calendar also handles February and leap years.

Calendar complication

What is a perpetual calendar watch?

A calendar that knows the length of every month and accounts for leap years, so it needs no correction until 2100.

How it works

An ordinary date watch counts to 31 every month and needs correcting five times a year. A perpetual calendar uses a mechanical memory, usually a cam called the program wheel that turns once every four years, to know that April has 30 days, February 28, and February in a leap year 29.

It typically shows the date, day, month and leap-year cycle, often with a moon phase. As long as it keeps running, it jumps from February 28 to March 1, or February 29 in a leap year, on its own.

The one thing it doesn't know is the Gregorian rule that years divisible by 100 aren't leap years unless they're divisible by 400. So the year 2100 will need one manual correction.

History

Perpetual calendars existed in pocket watches by the 18th century. Patek Philippe made the first perpetual calendar wristwatch in 1925, and its references 1518 and 2499 made the complication a collector's favourite. Kurt Klaus's 1985 IWC Da Vinci made it far easier to set, with every display adjustable from the crown.

Before you buy

If an automatic perpetual calendar stops, resetting it can take many presses of recessed correctors, so owners often keep one on a winder. Prices usually start in the low tens of thousands for Swiss mechanical versions; quartz perpetual calendars from Citizen and others cost far less.

Questions

Does a perpetual calendar ever need correcting?: Only in 2100, which isn't a leap year under the Gregorian calendar, and of course whenever the watch stops.
What's the difference between a perpetual and an annual calendar?: An annual calendar knows 30- and 31-day months but not February, so it needs one correction a year on March 1. A perpetual calendar also handles February and leap years.