In 2015, Biff steals the sports almanac

and takes the time machine

back to 1955, to give it to his younger self.

But as soon as he does that, he changes the future,

so the 2015 he returns to would be

a different 2015, not the 2015 that Marty and Doc were in.

This is Hot Tub Time Machine all over again.

If future Biff goes back to 2015

right after he gives young Biff the almanac,

he could get back to the 2015 with Marty and Doc in it.

Because it wasn't until his 21st birthday

that 1955 Biff placed his first bet.

SHELDON: Wait. Whoa, whoa.

Is “placed” right?

What do you mean?

Is “placed” the right tense

for something that would have happened in the future

of a past that was affected by something from the future?

Had will have placed?

That's my boy.

Okay, so, it wasn't until his 21st birthday

that Biff had will have placed his first bet

and made his millions.

That's when he altered the timeline.

Yeah, but he had will haven't placed it!

What?!

Unlike Hot Tub Time Machine,

this couldn't be more simple.

When Biff gets the almanac in 1955,

the alternate future he creates isn't the one

in which Marty and Doc Brown ever use the time machine

to travel to 2015.

Therefore,

in the new timeline,

Marty and Doc never brought the time machine...

W-Wait.

Is “brought” right?

Marty and Doc never had have had brought?

I don't know. You did it to me.

Oh, I'm going with it.

Marty and Doc never had have had brought

the time machine to 2015.

That means 2015 Biff could also

not had have had brought the almanac to 1955 Biff.

Therefore, the timeline in which 1955 Biff gets the almanac

is also the timeline

in which 1955 Biff never gets the almanac.

And not just “never gets.”

Never have, never hasn't, never had have hasn't.

He's right.