The NFL overtime rules state that a touchdown by either team wins the game (field goals and esoteric scoring methods are irrelevant to this question).
During Sunday Night Football on November 29, 2015, the Patriots lost to the Broncos in overtime when a Bronco scored a touchdown. This ended the game, 30-24.
During Monday Night Football on the next day, November 30, 2015, the Browns lost to the Ravens 33-27. The Browns lined up with seconds left to go in the fourth quarter and the score tied at 27. They were trying to hit a game-winning field goal as time expired. Instead, the field goal was blocked. The ball was in bounds and live, allowing a Raven to pick up the ball and run it back for a touchdown.
The clock was at zero by the time the ball was picked up, let alone run back. Coaches came onto the field, shook hands, everyone treated it like game over except for the referees. They made the Ravens attempt a PAT (or two-point conversion) due to the touchdown....