- Did you say 70 years?
- Yeah, 70 years, 2 months, 12 days to be exact.

5 seconds sound clip from the Back to the Future Part II movie soundboard.

You can hear this line at 01:39:37.088 in the Blu-ray version of the movie.

Quote context

[...]

- A letter for me? That's impossible.

- Who the hell are you?

- Western Union.

- Actually, a bunch of us at the office were kind of hoping maybe you could shed some light on the subject.

- We've had that envelope in our possession for the past 70 years. It was given to us with the explicit instructions that it be delivered to a young man with your description answering to the name of Marty, at this exact location, minute, November 12, 1955.

- We have a little bet going as to whether this Marty would actually be here. Looks like I lost.

- Did you say 70 years?

- Yeah, 70 years, 2 months, 12 days to be exact.

- Here sign on line 6, please. Here you are.

- It's from the doc!

- Dear Marty, if my calculations are correct, you will receive this letter immediately after you saw the DeLorean struck by lightning.

- First, let me assure you that I'm alive and well. I've been living happily these past eight months in the year 1885. The lightning bolt...

[...]