The appropriate question is, when the hell are they?
5 seconds sound clip from the Back to the Future movie soundboard.
You can hear this line at 00:22:33 in the Blu-ray version of the movie.
Quote context
[...]
- The temporal displacement occurred exactly 1:20 a.m. and zero seconds!
- Jesus Christ! Jesus Christ, Doc! You disintegrated Einstein!
- Calm down, Marty. I didn't disintegrate anything.
- The molecular structure of both Einstein and the car are completely intact.
- Then where the hell are they?
- The appropriate question is, when the hell are they?
- You see, Einstein has just become the world's first time traveler.
- One minute into the future, to be exact.
- At precisely 1:21 a.m. and zero seconds, we shall catch up with him and the time machine.
- Wait a minute. Wait a minute, Doc. (2)
[...]