Getty Images says:
Overall view of Wrigley Field taken during a game between the Chicago Cubs and the Philadelphia Phillies in September 1990 in Chicago, Illinois.
This narrows it down quite well. The Cubs and Phillies played only two games at Wrigley Field in September 1990, both afternoon contests: Wednesday, September 12 and Thursday, September 13.
More or less the same, right? Even the crowd sizes were similar: 16,258 on Wednesday, 15,495 on Thursday. And remember, those were actual turnstile counts, the National League didn’t switch to reporting tickets sold until 1993.