This is a legit question and I won't fight you on it if you go with January 3, 2009. I've actually wavered on this. My first thinking is that anyone can write any whitepaper they ever want to write, it's just an idea, let me see action. Jan 3, it was put into action. So, it seems like Jan 3 should be the birthday since that's when bitcoin really went live. But, then, since it did in fact go live, maybe Oct 31 was the real start. Maybe it's like conception, gestation period, then birth. Or just two birthdays so we can have two parties.