Used when someone prevents a problem from worsening or ends it completely. The computer crash threatened our project, but Tim saved the day by recovering the files.
Pro Tip 2/3
Last-Minute Win
Implies a solution arrives just in time, often unexpectedly, to prevent failure. We were going to lose the match, but Maria's goal saved the day.
Pro Tip 3/3
Under Pressure
Highlights someone's ability to act effectively despite being in a stressful situation. Under pressure, the pilot's quick decision saved the day for everyone on board.