L121.3

While standard moon-phase displays require adjustment every 2.5 years due to a 29.5-day approximation, the Lange 1 Moon Phase tracks the 29.531-day synodic month with 99.998 percent accuracy, requiring correction only once every 122.6 years. Its celestial disc uses varying blue shades to depict day and night, ensuring the moon orbits against a realistic background. Caliber L121.3 is derived from the 2015 caliber L121.