What does this idiom mean: "to save the day"?

[Rich7]

Test No. incompl/inter-38 "Save the Day", question 10

Despite all the problems and difficulties Charlie turned up at last minute and ......... the day.

(a) caught
(b) hit
(c) saved
(d) took

Test No. incompl/inter-38 "Save the Day", answer 10

Despite all the problems and difficulties Charlie turned up at last minute and saved the day.

Correct answer: (c) saved

Your answer was: correct
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save the day in other words please...

[Alan]

Meaning: find a solution/solve the problem.
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