Red-letter day  - A important，special day for some reason

March 4th is always a red-letter day for my wife and me.  3月4日永遠是我太太和我的特別的日子。

Today is a fantastic day for us - a real red-letter day! We've just been blessed with our first child - a beautiful baby boy!  今天對我們來說是美妙的一天 - 一個真正值得紀念的日子！承蒙主恩我們的第一個孩子剛剛誕生- 是一個漂亮的男孩！