... all-function advance pushbutton on the Lange adds practical value in a way that cannot be overstated for those who don't wear the watch every day. I have noticed this over the years with the older Langematik Perpetual, which has the same single-corrector feature. I am much more likely to wear the watch when I can mindlessly just push a single button with my finger 15, 30, 60, etc. times to set all the calendar functions correctly. I'd wear it much less often if I had to set each of the perpetual calendar functions individually.