When are you considered alive; when you are born or when you are conceived? 
It depends on who is doing the considering, of course. If you refer to everyone, then the answer is ‘both’.
I think the question is pretty much moot…from a purely scientific standpoint, the conceived embryo meets all the criterion for a life form. (I’m vaguely recalling from high school biology that there’s something like eight conditions for something to be a “life”…you know, consumes, respirates, cell division, etc.)
The issue you might be getting at indirectly is, where does “personhood” begin…unless I’m mistaken, and then I’ll just slink back to MPSIMS… 
The question seems to be “When are you considered a human being,” seeing how even cells are alive…
I thought this link (to a thread where the topic has been discussed before) might be helpful:
When does a human life actually start?
A conceptus is certainly alive, if only because it can die. But as others have pointed out this is generally considered a trivial question. The more difficult question is “when does a conceptus become a human person?”
What I’m getting at is, are we ALL nine months older than we think we are?
Parts of us, yes.
In some Asian cultures (some do this in China, I think), one’s age is indeed considered to begin at the date of conception.
I remember something like this from biology as well. I don’t know that ‘cell division’ is one of the criteria though (is a virus alive?..I don’t know myself). Imagine you created an incredibly complex robot or computer (e.g. Data from Star Trek or HAL from 2001). Is there a point where such a thing might be considered alive without the functions of respiration, reproduction and so on?
Unfortunately defining what exactly constitutes ‘life’ is a surprisingly difficult question. The most oft used example I’ve seen is that by many defined lists such as that described above fire might be considered alive (although I don’t think anyone believes fire is actually alive).
Sorry for the hijack…
More or less. They also think the nose is the first part formed, and thats where pointing at your nose from a side angle becomes an insult, especially with the Cantonese (meaning is that I am your ancestor, eg you are my illigitimate offspring).
In China, your age on official documents is from the date of birth. People celebrate different ages on occaision, and may or may not add a year.
Taiwan, at least in the 1980’s would add a year to someone’s age. I remember an overjoyed 20 year old calendar aged Taiwanese who discovered that he would be able to get into 21 and over bars in the US since his passport age was 21.
Age is counted from birth. It is called birthday, not conceptionday.