Yes, you are supposed to BD as close to o day as possible including the day of. This is because the egg can live up to 24 hours from the time it is released. Sometimes it is reccomended to BD the day after too, just for good measure.
Thanks you guys -- you're right, it can't hurt! I was just far from being in the mood and if it was a waste of time I would have rather just gone to bed! But we dtd just in case. And it's always fun once you get started... I'll let you know in a couple of weeks if it worked!