Why is it called Knight and Day?

Tom Cruise is Knight Cameron Diaz===Dia===is Day

It's a terrible title. A bad pun that doesn't in any way stand out. When they changed the title from "Wichita" (itself a bad title), they clearly couldn't think of a good one.

At least they didn't take some arbitrary adverb and attach it to some strong-sounding but largely irrelevant verb or noun. It was SORT of original.

I havent read all the comments here so this may already have been stated... but his real name of Matthew Knight is disclosed by his mother during the movie.

Seriously, people are having this much trouble with the title?

Night and Day means complete opposites. Knight is his last name so he is the Knight. Night and Day is in the fact that "June Havens finds her everyday life tangled with that of a secret agent". There's your Day reference; her life has started to merge with his...Day is becoming Night.

You don't have to name a person Day for it to make perfect sense. God, people want movies to read like kid's books without actually using their brains.

And no, I don't work for the company. I haven't even watched the movie yet and I already understand the damn title. Sheesh, people make me ill.

Near the end there is a mailbox with the name Knight on it. Roy's parents live there. So his last name really is Knight.

As explained numerous times, TC's name is actually Knight in the film. That's where the spelling comes from.

In my opinion the title is two fold:

First the differences between the two main characters were night and day, very well explained by matriarch_77 back on Thu Jul 1 2010 at 13:20:05. On Page 9 as I write this.

Second, the "differences" in the way Matthew Knight, the person that is with June Havens through-out most of the film, and Roy Miller, the CIA OP. while doing his job, is, once again "night and day." He was two different people in her eyes, and the differences in those two people were as different as "night and day."

Not saying this is correct, just my opinion.

It would appear few people got it and fewer people read the posts that explain it. It uses the pun, "like night and day," to describe people who are complete opposites, like the two main characters were. And Roy Miller's real last name is Knight, hence the addition of the letter 'K' at the beginning of the night and day pun.

Oh brother! It's a play on the meaning of being as different as night and day (he leads an exciting life full of danger, she not so much). Roy Miller's real last name is "Knight". You see the name on the mailbox at his parents' house. Everyone did realize that the older couple were his parents right? And that they think he is dead and he sends them money by having them win bogus lotteries, etc.? If her last name was Day or Daye that would have made the play a little more obvious but then that would have been a little corny, too. Oh wait, they needed to make it obvious, because obviously many people didn't get it.