That's right, Doc. November 12, 1955.
3 seconds sound clip from the Back to the Future Part II movie soundboard.
You can hear this line at 01:01:30.230 in the Blu-ray version of the movie.
Quote context
[...]
- Two McFlys with the same gun.
- Idiot.
- You're not gonna believe this.
- That's right, Doc. November 12, 1955.
- Unbelievable that Old Biff could've chosen that particular date.
- Damn! Got to fix that thing.
- All right. Time circuits on.
- What do you mean, time circuits on? Doc, we're not going back now!
- Yep.
[...]