Why does January and March have 31 days, and February 28? Why can’t/aren’t all 3 months 30 days each? (excluding leap year)
The Romans made the precursor to what our current calendar is, the julian calendar. It was 30 days each with extra days thrown in to make it 365. However February was always seen as an unlucky month so it was reduced. It’s just superstition.
it’s an interesting question and I don’t know how they (the Gregorians who created the calendar we currently most commonly use) chose which months to give extra days to, it does seem arbitrary but maybe there’s a reason I don’t know about.
One of the reasons why we have a wonky calendar at all is because it’s a Solar calendar that tries to maintain vestiges of a Lunar calendar that’s no longer really used. A Lunar cycle is 28 days. A moon phase is 7 days long. Weeks and Months are lunar units of time. A pure solar calendar would be divided into the 4 seasons (at the spring equinox, summer solstice, fall equinox, and winter solstice) only and months and weeks wouldn’t be a thing. We might say that today’s date (March 5th) is the 74th day of Winter in the current year.
Why do we have a Solar calendar but continue to use Lunar time units for scheduling? Tradition I suppose. Lunar calendars are older than Solar calendars. They’re also a natural biorhythm cycle for our species. Homo sapiens have an approximately 28 day menstrual cycle. That’s an interesting coincidence for sure, and maybe underlies some of the psychological importance of Lunar time keeping.
Because 365.25 (the number of days, i.e. rotations) it takes to go around the sun (the length of a year, i.e. orbit) is not divisible by 12 (the number of months, i.e. the number of lunar cycles, i.e. 12).