: why are some months 31 days or 30 days and why can’t they all be the same.
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We use a solar calendar, so one year is the length of time that it takes the Earth to orbit the sun – 365.25 days. With 12 months, you can’t have all the months have the same number of days, because 365 isn’t a multiple of 12. So at a minimum, you could go away with having 7 months at 30 days each, and 5 months at 31 days each.
But the reason that we have a 28 day month (February) goes back to the Roman calendar. The Roman calendar was 355 days, because it was a Lunar calendar – 12 lunar months, or 355 days. Roman superstition was that an even number of days in a month was unlucky, so they made every month either 29 days, or 31 days. Of course, you need at least one even numbered month in order for the total to be an odd number… so they picked February to be the unlucky month, and gave it 28 days.
We kept the convention when we switched from the lunar calendar to the solar calendar… now most months are 30 or 31 days, but February stays at 28.
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