02/29/2024

Why We Have Leap Years

Earth's calendar does not play out onstage

It would seem awfully hard to lose track of 0.24219 of a day. That not-inconsiderable amount adds up to five hours, 48 minutes and 20 seconds and if it were added to the clock in any 24-hour period, you’d surely notice it. But if the same span of time were spread out over the course of an entire year, it would be a whole lot easier to let it slip by.

That, in fact, is exactly what has happened virtually every year since the dawn of time. We are accustomed to thinking of the clockwork of the solar system as a very precise thing. The moon takes a month to orbit the Earth; the Earth takes 24 hours to spin on its axis and 365 days to orbit the sun.

But things are a little sloppier than that. A lunar month is actually 27.3 days. A single earthly rotation actually takes 23 hours and 56 minutes. And a single revolution takes a ragged 365.24129 days. Ever since humans began keeping calendars, that extra bit of orbital day has been a headache—and it’s the reason we came up with the concept of a leap year.

Please select this link to read the complete article from TIME.