Conversation so far:
Did Steve Young play any notable games while as a backup?
In their 1987 divisional playoff game against the Minnesota Vikings, he replaced Montana in the second half after the team fell behind 27–10.
Did Steve Young win the 1987 divisional playoff game against the Minnesota Vikings?
The 49ers still lost the game, but Young had a good performance, completing 12 of 17 pass attempts for 158 yards and a touchdown.
Did Steve Young play any other notable games as a backup besides the 1987 divisonal playoff game against the Minnesota Vikings?
On October 30, 1988, Young ran for a 49-yard, game-winning touchdown against the Minnesota Vikings.
Did Steve Young play any other notable games as a backup?
The Minnesota Vikings.

Question: When was this game being played?
Self-contained rewrite: When were the 49ers vs the Minnesota Vikings being played?