[drdec]

> On your sixth birthday we put a big 5 on your cake and call you a 5 year old all year.

If you are going to be that pedantic, I would point out that one only has one birthday.

(Well, unless one's mother is extremely unlucky.)

[naniwaduni]

"Birthday" does not mean the same thing as "date of birth".

[Detrytus]

“Birthday” is just short for “birth day anniversary”, I guess…

[copperx]

yes, birthday and birth day are different things. Just like everyday and every day have different meanings, and it isn't confusing (to most people).

[furyofantares]

Well regardless the number we constantly use is 0-indexed.