It has never happened in the same weekend until tonight. The only time it happened in the same week was 1994. The Vikings beat the Packers 13-10 on a Fuad Reveiz FG in OT on a Thursday night, followed by the Gophers 17-14 triumph in Camp Randall.
The Vikings failed to seal the deal in 1985 and 1965.
Typically, Vikings-Packers games are early in the season and in December, so the worlds don't collide all that often.