I'd make sure that day is one of the days from the TV show 24. You'd get a new thing accomplished every hour! If you've ever seen that show, it's insane! But I wouldn't be the president during the most previous season (Season 4)... where he (spoilers) gets attacked and blown up while on Air Force One (/spoilers).

So, from 12-1am, we would locate and thaw out the cryogenically frozen body of Ben Hogan.
From 1-2am, I would arrange the taxes so there are no loopholes and they don't favour the wealthy.
From 2-3am, I would rename Washington state, because it's too confusing between that and Washington D.C. (It would be renamed State in the North and West of the Country Because I'm Too Lazy to Think of a Name, or S.N.W.C.B.I.T.L.T.N.)
From 3-4am, I would focus on finally catching Osama bin Laden (and like the show - not realistically, but like the TV show would do it - we'd catch him within the hour).
From 4-5am, I would get a spy into the Saddam trial and get him/her to do to Saddam what his people did to the defense lawyer.
From 5-6am, I would arrange a meeting with whoever's in control of border policies, and basically close the borders, and make it harder for illegal immigrants to get papers.
From 6-7am, there would be a conflict at the border between Canada and S.N.W.C.B.I.T.L.T.N., which I would have to personally resolve.
From 7-8am, I would realize I'm late for my tee time with Tiger Woods, Jack Nicklaus and the cryogenically frozen, recently thawed Ben Hogan at T.P.C. at Sawgrass.
From 8am-1pm, I would be golfing at T.P.C. at Sawgrass with the 3 afforementioned people.
From 1-2pm, I would give an address to the country, outlining the various things I've accomplished so far, and give an agenda for my aspirations for the rest of the day.
From 2-3pm, I'd check my email.
From 3-4pm, I'd check Golf Rewind.
From 4-6pm, I'd sit back and watch Air Force One, while flying in Air Force One. :P
From 6-7pm, I'd locate the people who are psychotic enough to go out and kill their own children (any chlidren in general, but especially their own) and lock them up in an asylum for the rest of their lives.
From 7-8pm, I'd get a little nap. After all, I've been awake for almost two straight days by now!
From 8-10pm, I'd check up on the S.N.W.C.B.I.T.L.T.N.-Canada border situation, and make sure it's under control.
At 10pm, I'd watch Seinfeld.
From 11-12am, I'd watch a different episode of Season 3 of 24 on 24 separate TVs, all side-by-side, all at once, and I'd smile because they were the inspiration for my crazy, crazy Presidential day.

I dare anyone to beat that!