The 10 o'clock pushbutton on the Langematik Perpetual Calendar -- which is recessed on all the later versions but is large, rectangular, and protruding on the yellow gold and earliest platinum models -- advances all calendar functions by 1 full day with a single push. This is a wonderful, convenient feature that Lange salespeople were not trained to highlight back when this watch was being marketed and sold, so it's not often discussed. For someone like me, who wears the watch very infrequently, this feature is (by far) the most enjoyable functional aspect of this complicated watch: I just push this one button many times, and I never have to reset any of the individual calendar functions.