In the opening credits, it states that it is 12 pm on a Friday, but in that first scene Mac and Dennis begin chanting about their "movie night" and Dennis chants, "Tuesday night's movie night!"
After Mac and Dennis throw cups of water at each other in the restaurant, a large water stain is visible on Dennis' shirt. After the manager comes to tell them to leave, the water stain is significantly smaller on Dennis' shirt.
The man seated behind Dennis is hit with the water that Mac throws at him, yet he says/does nothing about it.