A fully automatic calendar which automatically adjusts the end of each month, including the months of a leap year until February 28, 2100.
The perpetual calendar watches are some of the most amazing time pieces that the world has ever seen. They have a memory in the watch of 1,461 days. That is four years including a leap year. This is incredible, and most of the nice watches will not have to be reset, till 2100, only because the Gregorian Calendar stipulates that there will be no leap year in 2100. There are many faces of perpetual calendar watches. These make great looking watches.
The other really cool style for perpetual calendar watches are the retrograde systems. They are very appealing to the eye, and some even have the old classic jump hour feature as well. Some watches like the A. Lange & Sohne Perpetual Calendar watch have the time on side and the day of the week on the other side.