According to Retrosheet, who tend to know what they are talking about, the game was on July 31.
July 30 - Witt gets the win
http://www.retrosheet.org/boxesetc/1...300MIL1990.htm
July 31 - Ryan gets the win
http://www.retrosheet.org/boxesetc/1...310MIL1990.htm
Doug
PS -
Just a comment, my opinion could be completely worthless, but I hate season passes for every game of a season being marked as a specific game. I'm trying to come up with a witty analogy, but suffice to say I just think it's stupid. But, there are a lot of things about the people who get paid for their opinions that I find stupid.