Wow I never thought about this that much! 4 sept 2012 is my date, but I think I did drink past midnight the night before--really can't remember between the lying on the floor crying, calling my boyfriend, and heaven knows what else. I think I also may have had a sip of beer the next morning. I do remember opening an oil can of foster's and staring at it for a long time, then pouring it out. I'm thinking I didn't drink any because one swallow and I don't think I would've stopped....
I agree it doesn't really matter. It's a personal thing. I guess I could say my sobriety date is "on or around 4 sept"