A weekly calendar is a complication that shows which numbered week of the year it is, as well as the day and the date. In Patek Philippe’s version, the movement shows the week number together with the month it belongs to, so each week can be read alongside its month.
How are the weeks counted?
The Patek Philippe ref. 5212A follows the ISO week-numbering system. Under this system, each year’s first full week must start on a Monday. The first week of the year is the one that contains 4 January. The weeks are then counted on from there. Because of this rule, the count does not always stop at 52. Some years have 53 weeks instead.
How does Patek Philippe’s weekly calendar work?
The Calatrava Weekly Calendar ref. 5212A was launched in 2019. It was the first Patek Philippe watch to show the week number. Inside, the week module uses asymmetric wheels. Their teeth differ in length and are set up for the weekly cycle. On the dial, red-tipped hands show the week number and the day of the week. The day and the week number can each be corrected on their own. One pusher sits at 8 o’clock and the other at 10 o’clock.
How do other makers show the week?
Blancpain’s Villeret Semainier marks the week number around the edge of the dial. A blued serpentine hand points to the current week. The scale runs from 1 to 53. The week number changes as Sunday turns into Monday. The A. Lange & Söhne 1815 Kalenderwoche also places the week on the outside of the dial. There, the week of the year is shown on the outer ring.
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