Watch mechanism in focus: Calendars
Monitoring the date, day and month through your timepiece is possible through the creation of two calendar complications -- the perpetual and annual calenders.
IWC Schaffhausen Da Vinci Perpetual Calender
While a date display (whether in an aperture or in a separate dial) is the simplest complication to be included in a timepiece, it can be quite troublesome for a watch owner to constantly adjust taking into considerations there are leap years and irregular number of days per month.
In the case of most timepieces, the watches will be set with a 31 day cycles for a full month, so in months with 30 days, watch owners will then have to take the extra effort of adjusting it.
With the advancement of technology, watchmakers have since developed two advanced complications: the perpetual calendar and the annual calendar.
These calendar functions serve to monitor the calendar functions in a timepiece more accurately and ensure the date does not have to be adjusted every month.
This is more convenient because as long as the watch is wound and working, the calendar complication will be functioning at tiptop form.
How do you tell a perpetual calendar and an annual calendar apart? We will share how.
But first, let’s look at the difference both calendar complications share:
- Both watches often display the hour, day, date and month.
- Both functions are based on the Gregorian calendar, an internationally accepted civil calendar that we adhere to as well.
IWC Schaffhausen Annual Calender Calibre (left) vs Perpetual Calender Calibre (right)
Annual vs Perpetual
A watch with an annual calendar needs to be manually set once a year while the perpetual calendar does not.
To explain, an annual calendar is often automatically adjusted to follow months that are within 30 to 31 days. This means that an annual calendar does not recognise that February has 28 days or 29 days for leap years. An extra step of manually adjusting the date on the 1st of March every year is required every year.
In comparison, the perpetual calendar does not require this extra step. With a combination of difference levers and movements, a perpetual calendar will automatically change to the correct date, including from February 28th or 29th to March 1st. The extra complication required to power a perpetual calendar means that often, a timepiece with perpetual calendar is often more expensive!
(Photos: IWC Schaffhausen)