red-letter day
noun /ˌred ˈletə deɪ/
/ˌred ˈletər deɪ/
- an important day, or a day that you will remember, because of something good that happened then
- birthdays, wedding anniversaries and other red-letter days
- It was a red-letter day for United, who won a place in Saturday’s final.
Word Originearly 18th cent.: from the practice of highlighting a festival in red on a calendar.