In Ancient Rome, most months were 29 days. Even numbers were seen as unlucky, and when February was added to the calendar, a day was removed to prevent a year with an even number of days.
I’m not complaining that the dullest, coldest month of the year only has to lasts 28 days (sometimes 29), but I’ve always been curious why.
Back in ancient Rome, the precursor to the modern Gregorian calendar had 10 months, March through December, that roughly synced up with the lunar cycle. All months had 30 or 31 days and covered 304 days total. After the end of December, they didn’t feel the need to keep track of months.
At the time, Romulus, the first king of Rome, and his people found the time between December and March to be unimportant because it had nothing to do with the Harvest.
Around 750BCE Emperor Numa Pompilius decided to add 2 months (January & February) to the calendar to sync it up with the 12-cycle, ~355 day lunar year.
Even numbers were considered unlucky to the Romans, so he wanted to make all months 29 or 31 days. However, 12 odd-numbered months would add up to an even-numbered year, which would be even unluckier.
Having to make one month “unlucky”, he decided to remove a day from February. No one is entirely sure why February was chosen, but there are several theories.
Obviously the calendar has been changed since then, as it now counts 365 (or 366) days and follows the pattern of seasons and the solar cycle, but when the calendar was reformed by Caesar, the length of February was not changed.
If you’re interested in how the Romans handled a year that didn’t line up with the seasons and/or how it was eventually changed, check this out.