A. LANGE & SÖHNE | SAX-O-MAT A WHITE GOLD AUTOMATIC ANNUAL CALENDAR WRISTWATCH WITH MOON PHASES, CIRCA 2005

Known for being the first automatically powered perpetual calendar wristwatch, the Langematik is arguably one of greatest interpretation of the perpetual calendar function ever made. With its striking oversized date windows, the watch is equipped with an uncommon continuously moving moon phase disc which provides far greater accuracy than the jumping-disc styled moon phases other brand uses, it is also geared with a patented Zero-Reset mechanism that allows efficient synchronization of the time. Once correctly set, the date display remains accurate until the next secular year occurs: On 28 February 2100, it will need to be advanced by only one day. The moon phase mechanism is also stunningly accurate: after 122.6 years of uninterrupted operation, it deviates from synodic lunation by merely one day.

Lange's patented "zero-reset" mechanism simplifies the synchronization of the watch with a time signal. When the crown is pulled out, it automatically causes the seconds hand to jump to the 12 o'clock or "zero" position.