What is an Annual Calendar? / Spring Wisdom - Answering your watch questions

Q: What is an annual calendar?

One of the complications that many manufacturers have been working on recently is the annual calendar, which has the advantage of being easier to use than a regular calendar and less complicated than a perpetual calendar.

A: It is a calendar that automatically advances the days of short months, except at the end of February.

Specifically, if you manually adjust the calendar at the end of February on March 1st, the date will automatically be adjusted for the rest of the month. Patek Philippe was the first to perfect this annual calendar, and many other manufacturers followed suit, including Omega and Rolex.

However, most of the early annual calendars, except for those made by Patek Philippe, were simple perpetual calendars, which made them expensive.

However, Dr. Ludwig Oechslin perfected a simple annual calendar consisting of only gears. This meant that the ETA 7750 could be turned into an annual calendar by simply adding a few parts. Since then, Zenith and other brands have adopted Oechslin's simple annual calendar mechanism.

There are also semi-perpetual watches that require manual adjustment only once every four years.

A similar device to the annual calendar is the semi-perpetual calendar, which only requires manual adjustment of the last day of February in leap years. While the semi-perpetual calendar only needs to be adjusted once every four years, unlike the annual calendar, which requires adjustment of the last day of February every year, it is mechanically almost the same as a perpetual calendar. For this reason, there are currently very few manufacturers that use semi-perpetual calendars, with the exception of Breitling.