Save the day:

　　反败为胜;挽救局面

　　例句：

　　The team was expected to lose, but Sally made three points and saved the day.

　　本来打算会输的，但Sally进了个三分球，最后反败为胜。

　　Late in the day:

　　为时已晚;坐失良机

　　例句：

　　①What with one thing and another, it was fairly late in the day when we returned to town.

　　忙完这个又忙那个，等到我们回到镇里的时候，天色已经很晚了。

　　②It's a little late in the day to start talking about policy changes.

　　现在开始谈论改变政策，已有点为时过晚。

　　A black day:

　　倒霉的一天;黑暗的一天

　　例句：

　　When we heard the news that David had died, we knew it was going to be a black day for all of his loyal fans.

　　当我们听到大卫去世的消息时，我们知道对他所有忠实的粉丝来说这将是黑暗的一天。