Computus

Computus is a fancy word that means figuring out when Easter happens. It's a bit tricky because Easter is always on a Sunday, but the day changes every year! So how do we figure it out?

Well, there's this thing called the lunar cycle - that's when the moon goes through all its different phases (like full moon, new moon, crescent moon, and so on). And then there's the solar cycle - that's when the Earth goes around the sun once.

So, to figure out when Easter happens, we need to use both the lunar and solar cycles! The rule is that Easter happens on the first Sunday after the first full moon after the spring equinox (that's when day and night are equal and spring officially starts).

Now, that might sound a bit confusing, but it's actually pretty simple once you break it down. Every year, we can look at a calendar and figure out when the spring equinox happens (usually around March 20 or 21). Then we just wait for the first full moon after that, and then count the number of days until the next Sunday. That Sunday is Easter!

So, that's basically what computus is - figuring out when Easter happens by using the lunar and solar cycles. It might seem a bit complicated, but it's actually a really cool way of combining science and religion!