What is meant by the expression "Save the day"? Does It mean to take advantage of the day? Could you provide some examples?
"Save the day" is an idiom. It doesn't mean to take advantage of the day. If somebody saves the day, he does something to successfully prevent a likely defeat, failure, or unpleasant situation. For examples:
We are expected to lose the game, but our tailenders (lower order batsmen) played well and saved the day.
The police saved the day by coming just in the nick of time and catching the kidnappers.
We forgot to bring a knife for cutting the wedding cake, but Peter brought one and saved the day.