For CNN, Amy O’Kruk and Kenneth Uzquiano asked what would happen if we didn’t have leap years. Without the extra day every four years, we’d eventually have seasons time-shifted by half a year.
Also, because the exact time it takes the Earth to orbit the sun is just under a quarter of a day, leap year adjustments are slightly off. We’ll have to adjust by one day every 3,333 years. I never thought about it, but it makes sense.