Gregory's Server@CuriousCat @kityates
Well as I had to google for it, here you go :
short :
"Because Oct 31 represents the octal (base 8) number 31, which, when converted to decimal, is 25. Dec 25 is short for Decimal 25, thus the two are equal."
long :
https://www.idtech.com/blog/part-i-top-10-programmer-jokes-explained-for-the-rest-of-us
cheers
@johannbourquenez @kityates thank you. At first I thought I was being dense, but remembered that if I don't understand, there are always others like me.