Taylor Swift 's new album is coming out October 3, the same day Diddy is set to be sentenced in his federal criminal case ... which is interesting, 'cause T-Swift once said she'd go to prom with the guy in a group!

A clip from a 2011 interview from "The Rachael Ray Show" has resurfaced in the aftermath of Swift revealing her album release date , where Taylor selects her ideal prom date from a choice of a group of celebs.

Taylor says she'd rather go with a group than a specific date ... picking up photos of Jennifer Lopez , Justin Timberlake , Katy Perry , Sheryl Crow -- and, finally, Diddy.

Diddy's always been nice to her and he'd be super fun as part of the group date, Taylor says ... and, Ray agrees -- calling the guy a "gentleman."

Diddy had a ton of ce

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