Watch Donald Trump's 9/11 Screwup ... Not So Convenient

Donald Trump confused America's darkest day with America's favorite convenience store -- totally honest mistake, except it happened as he was trying to sway NY primary voters. Big oops?

Trump was at a rally in Buffalo Monday night and started talking about 9/11 and where he was in NYC when the Towers came down. But apparently he had Slurpees on the brain because he ended up talking 7/11 instead.

Check it out ... to his credit, the Donald never missed a beat.

We doubt Trump's seen the inside of any convenience store in, oh ... forever, but he could try spinning this as he's a man of the people.