The calendar transmission system of Tudor watches is a time-wheel transmitted type. The time wheel meshes with the day-crossing wheel segment, and the day-crossing gear shaft meshes with the date-changing wheel. After two-stage deceleration transmission, the reduction ratio is determined. The number of teeth on the meshing gears are as follows: the time wheel has 27 teeth, the crossing wheel segment has 21 teeth (6 cross teeth, 14 teeth), and the date-changing wheel has 36 teeth.
(2) Calendar Control System: This control system is relatively simple, using a semi-circular elastic spring riveted integrally with the date-changing wheel, which serves as an elastic finger. However, since it does not store energy, it is referred to as a "slow-climbing" type. The day-changing time takes approximately 1.5 hours. When the hands are manually turned backward, the finger can radially displace due to the action of the calendar ring's teeth, preventing the calendar ring from reversing or shaking.
(3) Calendar Positioning System: It consists of a knife-shaped positioning rod and a positioning rod spring, ensuring the reset and positioning of the calendar ring.
(4) Calendar Display System: A thin calendar ring is used, with a triangular shape. The calendar ring is positioned radially by the main plate's circular platform and inner teeth, and axially by the main plate's coffin and two pressure plates.