technically aren't we 9 months older?

Some cultures actually calculate age that way.

I've never thought of that! But I don't think so. Because we aren't fully developed or actually see/experience life until we are actually born.
But if that were true then I'd be 18 already! :D

No, your birthday is a celebration of one's BIRTH. Being a year old means we came out of the belly a year ago.

Nope. We are born once we are out the womb and developed

Yes, this is a good thought.

I guess. The Japanese count you as 1 when you're born. So according to them you should be age 2 three months after birth. x

that dont count. it counts from when we came out of the womb.

Your date of birth is when your age is usually counted from, hence its anniversary (when you hit a year old) being called a "birthday". These measurements are really just man made, so it doesn't make much difference. Besides, it can be hard to pinpoint the exact date of conception, and most people don't spend exactly nine months in the womb.

Yes. But it's sometimes difficult to establish the precise conception date, and celebrating a time when your parents were actually having sexy times isn't so fun for kiddies or older kiddies to contemplate.

Edit: Yes, we celebrate our BIRTHday, but the question is about our age, not what we call the celebration

plus a few days when you were just an egg in your mom's ovary.