save the day

save the day (third-person singular simple present saves the day, present participle saving the day, simple past and past participle saved the day)

1. (idiomatic, sometimes humorous) To rescue a person or situation from imminent danger or major failure.
   • 1881, Horatio Alger, chapter 25, in From Canal Boy to President or The Boyhood and Manhood of James A. Garfield:

     [H]e acted as chief of staff to General Rosecranz, aiding his superior officer at a most critical point in the battle by advice which had an important influence in saving the day.

   • 1912, Arthur B. Reeve, chapter 6, in The Poisoned Pen:

     “It's Paddy,” cried Craig. “If he can bring them all out safely without the loss of a life he'll save the day yet.”

   • 1991 June 24, John Skow, “Life In The Age Of Lyme”, in Time‎:

     An effective vaccine would save the day and last year researchers at Yale were reporting some progress.

   • 2008 May 28, Eugene Robinson, “The ravages of the Clinton campaign”, in San Francisco Chronicle‎:

     Maybe a strapping woodsman will come along and save the day.

• Often suggestive of a rescue executed in a valiant or heroic manner, and sometimes used ironically to indicate that the rescue was not particularly heroic or the situation not particularly dire.