Halloween is celebrated on October 31^{st} and Christmas is on December 25^{th}. There is absolutely nothing in common between these two dates but only for a non-programmer. For a non-programmer mixing up these two dates makes absolutely no sense but that is not the case with a programmer. For a programmer it is a practical joke! Want to know why? Then let’s understand why programmers mix up Halloween and Christmas.

Programmers mix the two dates because for them Dec 25 is Oct 31. For you these are just two monthly dates but to a programmer it can mean something entirely different. Dec 25 is an abbreviation for Decimal 25 and Oct 31 is an abbreviation for Octal 31. If you are thinking why, then go back to the decimal number system.

What is Decimal? Decimal is a simple way of counting which you use in day to day life or you can represent them as numbers in blocks of ten. In our daily life you use numbers from 0 to 9 and after that you go to 10, 11 and so on. After 99 there is another block of 10, 100 then 101 and it continues.

So, in decimal system after 10 you generally use a different manner to represent higher number like 25 can be written as 2*10+5 or 31 as 3*10+1. Now what actually you do in octal system? In Octal system you count the numbers till seven like 0, 1, 2, 3, 4, 5, 6, and 7. When you come to 8 it is represented same as the decimal 10. So, like in decimal the numbers are represented as the multiple of 10 and in Octal the numbers are represented as multiple of 8. So, for a programmer 25 in decimal 2*10+5 is same as 31 in octal 3*8+1.