... between the Saxonia AC and the Langematik PC: When you push the corrector button at the 10 o'clock position on the PC, every function (day/date/moonphase) advances by 1 full day. Because of this, you literally never have to reset any of the individual calendar functions if you stop wearing the watch for a while. You just push that one button once for each day that passed since the watch stopped. When you push that same corrector button on the AC, only the date advances.
Even with that difference, though, the Saxonia AC is a truly beautiful (and more legible) watch!