When Does "Thelma & Louise" (1991) Take Place?
"Thelma & Louise" is a comedy crime film written by Callie Khouri that released May 24th, 1991. So when is "Thelma & Louise" set?
It takes place in the year:
We know this because as Louise Sawyer is leaving her job at the diner very early in the movie, she passes a vending machine for the newspaper "USA TODAY", which was first published September of 1982 AD. So it must be after September of 1982 AD.

1991 AD
We know this because as Louise Sawyer is leaving her job at the diner very early in the movie, she passes a vending machine for the newspaper "USA TODAY", which was first published September of 1982 AD. So it must be after September of 1982 AD.
Also, when Harlan Puckett slumps onto the back of a parked truck at about one-sixth through the story a car inspection certification expiration date sticker can be clearly seen reading "92" for 1992 AD on the Arkansas license plate. Arkansas repealed their 1978 AD law requiring automobile inspections in 1997 AD so it is most likely before 1997 AD.
Furthermore, car inspection certification expiration stickers were only good for 1 year ("at least once annually") when they were required in the state, placing the story in 1991 AD at the earliest.
More specifically, at nearly halfway through the narrative Jimmy Lennox is holding a newspaper sports section which contains the headline: "Phillies retire Schmidt’s '20' ", referring to the ceremony held on May 26th, 1990 AD at which the Philadelphia Phillies third baseman Mike Schmidt was honored upon his retirement by having his uniform’s number 20 permanently retired from use by the team.
If this newspaper were 100% certainly new, this would contradict the sticker on the truck’s license plate but it’s not impossible this newspaper section has been hanging around for 6 months. It is most likely very early 1991 AD.