The phrase "to save the day" means to rescue or solve a problem or difficult situation, often at the last moment, and bring about a positive outcome. Full definition
So can a career in trucking save the day for many of these factory workers, construction workers, salespeople, retailer workers, and other job loss victims across the board? (truckingtruth.com)
The tenant will see what the increase would have been if you didn't save the day by lowering it. (thelpa.com)
Really saved the day with my teenage boy who has wanted something like this. (theurbanposer.com)