HELP!!! Blog Birthday...

I have a question, might sound funny or silly, but this is a genuine question.

I want to determine what is exactly my blogger birthday. Or rather, what date should I consider as my blog birthday?

• My first post was on 8th December 2009.
• I go and look at the Stats in "all time" view, it starts at May 2008.
• I go to blogger profile, it says - "Blogger since June 2007.

So, either tell me a way I can know to find my blog birthday. Or tell me from the above 3 dates, what should be my blog birthday.

Thanks!