We all know that every 4th year is a leap year right?

And how do you know which year that is? You divide the year (without the Century) by 4. If it goes exactly, then that’s a leap year. Right?

Wrong!

OK, so 2020 was a leap year because 20/4 = 5 exactly, and 2024 will be the next leap year because 24/4 = 6 exactly.

But, what about 2000? Was that a leap year? No it wasn’t, because every 100 years, we have to skip a leap year.

Now, why is that? It’s because nature is not quite as co-operative as we would like. So, a year is actually 365.24 days.

If it was 365.25, or 365 and a quarter, then there would be no problem, but that .01 (100th) means that by every 100th year, we would be one day too long, so we have to miss the leap year that year.

The fact that we do it in the 00 years is not relevant, but it’s done then because it’s easy to remember.

So do we have the same problem with the hours in a day? Are there exactly 24?

Yes, there are. Why? Because the earth always spins at the same rate (well, almost always), and we define a day as the amount of time it takes to complete one revolution, so it’s spot on.