InParticular, I have always done that too - doing things in blocks of hours. Not so much with regard to not drinking for me, because I'm cool with that now, but with other things too .. (like going to the in-laws - LOL ... well, they're ex-in-laws now, so I don't have to go .. but that's another story!)
I like doing that. It really puts the timing of the occasion into perspective. Just a few hours. And then, afterward, it will be a great feeling to say, "I'm still sober .. I did it .. I didn't need the drinks" ... and next time will be even easier.