|housing diameter:||43 mm|
|housing height:||16 mm|
Not surprisingly it is an alarm that will count backwards until it reaches zero. So instead of setting it to a certain time then, you can set it to go off in a certain amount of time staring from now.
A perpetual calendar is a calendar that will give you the day of the week at any date in any year. So it would tell you for example that January the 11th in 2023 is a Wednesday. This works because the only part of the day and date never repeats itself: the year. Days, weeks, months all keep repeating themselves throughout their cycle. This can be used to fit a calendar into a watch that will continue to proceed through these cycles and never run out. Plus it gives you the day of the week.
Water tightness or impermeability, surprisingly enough, is the degree to which you can expose your watch to the element water. A watch can be water repellent to a variety of degrees, from surviving the odd splash, to keeping the watch fully functioning long after your crushed body has hit the ocean floor. Please note that these are always theoretical values. Water behaves very differently at different temperatures and with varying salinity. So we took our crayons and made you this rough guide (which, by the way, is in no way legally binding and we will not be held accountable for your watch if you ruin it)::
FYI: 10m is 1 bar is (roughly) 33 ft is (exactly) 0.986923267 atm