red-letter day

纪念日，喜庆日子

这个隐喻来自日历：每逢节日包括宗教日，日历都印红色。



例：

It was a red-letter day for me when I landed in America and entered school there.

这是我到美国入学的纪念日。

Next Sunday is a red-letter day when they are going to be married.

下星期日是他们结婚的大喜日子。