Having dealt with dates and time in programming context for many years, I have realized what a nightmare our common calendars are, and how much they vary by the year/month/etc.
Yet there are fully mechanical watches which have a little "day number" window saying something like "1" (for the 1st day of the current month) or "27" (for the 27th day of the current month).
How is this possible? Not only do the number of days vary between the months, but it seems much more complicated than that, with certain years having more days and all that nightmarish stuff you don't want to deal with even in software code -- let alone mechanical parts!
Have I misunderstood something fundamental about the calendar system in common use today? Are these watches ultra-complex inside with all sorts of cogwheels dedicated solely to keep track of these differences? How does the watch know (or how can it be told) what the current year (or even month) is, so that it can display the correct day?
Most of the mechanical watches I've seen only display the current day number -- not the month and the year. So this really confuses me in multiple ways.