31 Dec = 25 Oct

Warning: Extreme geekiness ahead

A random stranger retweeted one of their random strangers, in the typical way that Twitter does, the peculiar riddle of how they can say "Merry Christmas" on Halloween. It turns out that 31 Dec = 25 Oct. And it does. Here's why.

Well for starters, there's a bit of schenanigans going on. This particular piece of recreational mathematics doesn't actually concern dates, but rather the mathematically concept of Bases.

We normally work in base 10 or decimal. That is, there are 10 digits to count with before you start adding one to the next position to the left, i.e. 1,2,3,4,5,6,7,8,9,10

But you can work in different bases by either increasing or decreasing the number of possible digits we can use. 2 common ones in computing are base 2 (binary: 0,1,10,11,100,101) and base 16 (hexadecimal 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,10).

The cheat with this riddle is that rather than it meaning 31st October and 25th December, it's using maths shorthand for saying 31 in Oct (octal = base 8) is equal to 25 in Dec (decimal = base 10). So it's nothing to do with claiming an equivalence between the second most important day of the Christian calendar and what I'd guess would be the second most important day of the Pagan calendar.

I warned you it was geeky. And very similar to a solution to how the question and answer of Life, The Universe and Everything actually works out fine.