The big date display has been a hallmark of the Glashütte-based A. Lange & Söhne since it was re-established in 1994. In 2016, Lange introduced a new Saxonia model that combined an outsize date with an extremely precise moon-phase display. The ultra-precise moon-phase display also has a long history with the brand: the movement in this watch, the self-winding Caliber L086.5, is Lange’s 16th movement with this feature.

The big date window and moonphase are arranged symmetrically beneath the dial

Just how precise is the moon-phase? It will be off by one day in 122.6 years (assuming, of course, that the watch is kept running continuously for that time). The display is connected to the hour wheel and is always in motion. Thanks to the precisely calculated seven-step gear train, the period between one new moon and the next is 99.998 percent accurate. If you do allow the watch to stop running, you can adjust the moon-phase display by pushing the button set into the case at 4 o’clock. The moon disk is made of gold and decorated with 852 laser-cut stars. The disk’s intense, deep-blue color is created using a special patented coating process. The moon-phase display shares its subdial with the seconds indicator.

Caliber L086.5 is based on the L086.1, which was introduced in 2011. The new caliber is 5.2 mm thick, just 1.5 mm thicker than the base caliber, despite the addition of the calendar and moon-phase. The movement has a 72-hour power reserve, supplied by a single barrel.

The caseback reveals the new Caliber L0865.5

Like the moon-phase display, the movement itself is extremely precise. When we put the watch on the timing machine, the deviation was less than 0.5 seconds per day. On the wrist, the watch deviated by just 1 second per day. Lange follows very strict standards when it adjusts its movements. They must lose no more than 2 seconds a day and gain no more than 3 seconds. These tolerances are twice as tight as those required for COSC certification. For watches with long power reserves, Lange’s standards allow an additional full second of deviation after 50 to 60 hours. The watch met this standard as well.

The watch’s balance spring is manufactured in house and works in conjunction with a screw balance. The balance’s frequency is 21,600 vph (3 Hz). The lateral screw on the swan’s-neck regulator, a common feature of watches made in Glashütte, is used to adjust the rate. A look through the transparent sapphire caseback reveals other details associated with Glashütte watchmaking: a hand-engraved balance bridge, three-quarter plate made of untreated German silver, and blued screws. The winding rotor has a platinum weight on its outer edge to provide more winding efficiency.

The date is located prominently on the dial, directly below the 12 o’clock marker. The display is framed by a gold double window with a center bar. The moon-phase/small seconds display is eye-catching, not just because of the moon and stars but also thanks to the Arabic numerals at 20, 30 and 40 seconds. 
Lange has recently made some changes to the Saxonia’s dial. The gold baton-shaped markers now extend to the edge of the dial rather than ending with a dot as before. The minute-track markers are also longer, for a more modern look.

Note the "ones" disk and a "10s" cross-shaped disk on the big-date displayOUTSIZE DATE: The watch’s big-date display consists of a “ones” disk and a “10s” cross-shaped disk that are spaced only 0.15 mm apart. The “ones” disk advances once per day except when the date changes from the 31st to the 1st. Two teeth are omitted so the digit remains in place for this period. The cross-shaped “10s” disk advances one step every 10 days. Only for the 30th and 31st of the month does the cross need to advance after just two days so that the “10s” window is blank at the start of the month. The cross has a four-toothed cam that enables it to skip forward at the correct time.

The moon-phase is accurate to 122.6 years ULTRA-PRECISE MOON-PHASE: The moon disk moves continuously, powered by the rotation of the hour wheel. The seven-step transmission is calculated to precisely reflect the synodic lunar month of 29.531 days: the display is 99.998 percent accurate from one new moon to the next. If the watch were to run continuously, the moon-phase display would deviate from the actual position of the moon by a single day every 122.6 years.