Alex Hamilton’s fifteenth lesson covers the mechanics and servicing of watch calendar systems, from simple date displays to complex day-date complications. He explains how the 24-hour cycle is achieved by reducing the hour wheel’s twice-daily rotation through intermediate and driving wheels. The tutorial compares the engineering of Seiko’s plastic, often unlubricated components with ETA’s spring-loaded, brass systems, providing specific lubrication and troubleshooting advice for each. Hamilton also clarifies the “danger zone” (typically 9 PM to 3 AM) for quick-setting the date, demonstrating how modern safety features like spring-loaded fingers protect the movement from user error.
