It's Thursday. It's day 23. I watched that movie again. And today I review some Rotten Tomatoes reviews as well as read some full reviews of Back to the Future Part III from back when it first came out:

Review/Film; A Trilogy Whose Future Has Passed
By Vincent Canby
May 25, 1990
New York Times (via the Internet Archive)

Back To the Future Part III
By Ty Burr
Updated November 09, 1990
Entertainment Weekly

Back To the Future Part III
By Variety Staff
December 31, 1989
Variety

Back To the Future Part III
By Jonathan Rosenbaum
October 26, 1985 (cute, but that can't be right)
Chicago Reader

Back To the Future Part III
By Hal Hinson
May 25, 1990
Washington Post