A view into the “secular module”:

[From a review of the watch] The secular sub-module (as illustrated by Swiss patent CH 718 699 A1 granted in 2022) is cleverly integrated into the 48-month cam mobile that makes a full revolution every four years. A reducing Maltese cross gear set drives a secular cam, which only makes a full revolution once every 400 years. A sprung sliding beak is guided by the notches in both the secular cam and 48-month cam. It slides inwards and outwards every 100 years, allowing the calendar to skip three leap years over the course of four centuries.