eli5 What is the concept of months? Why Feb has only 28 while some have 31? When did the concept of 365 days’ year come in people?

Question

eli5 What is the concept of months? Why Feb has only 28 while some have 31? When did the concept of 365 days’ year come in people?

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Answer 1

365 days is a year because that’s how many days it takes for the earth to rotate to the same spot in its orbit around the sun. It’s useful to track things this way to aid in farming and you track natural, seasonal phenomena. We have leap year (where we put in 1 extra day) because it’s not exact.

Each month is roughly the time it takes for the moon to make one rotation around the earth (about 12.3 times per year). Again, useful to track things this way for natural phenomena (though less so than years). Some early civilizations had 10 months instead. A blue moon, a special celebration, is when we get two full moons in 1 month. You can’t evenly split 365 into 12, so you get uneven numbers of days, though I’m sure there’s a specific reason for February being so much noticeably shorter.