Several date displays?
The word perpetual in the name of A. Lange & Söhne Langematik Perpetual stands for perpetual calendar. Despite its origin in the German glassworks, this is English and means perpetual calendar, because the A. Lange & Söhne Langematik Perpetual was the first watch to have a perpetual calendar and a separate large, easy-to-read date display when it appeared in 2001. The latter can still be found on today's models in Arabic numerals directly below the twelve o'clock mark. To make room for them, the A. Lange & Söhne logo was adapted for the Langematik Perpetual. It stands directly below the display and the otherwise arched company name is kept straight.
The perpetual calendar
Accurate time measurement over many years is not easy. In order to correspond to the course of the planets, even the modern calendar still has to insert leap years. The A. Lange & Söhne Langematik Perpetual has a mechanism that takes this into account. If you keep it running for so long, you won't have to make a manual correction to your watch until 2100. To prove this, the A. Lange & Söhne Langematik Perpetual displays the day of the week on the lower left of another dial and the month on the lower right.