red letter day

Noun

red letter day (plural red letter days)

1. A day marked in red on calendars; a church feast day.
   • The only red-letter day occurring in July, is the twenty-fifth, called St James's Day.1825, Christian Gleaner and Domestic Magazine, Volume 2, page 161
   • But the monsters who interrupt men in the middle of a sentence are to be found everywhere; and they are always practising. Red-letter days or black-letter days, festival or fast, makes no difference to them.1893, Thomas De Quincey, “Conversation and Coleridge”, in Alexander H. Japp, editor, The Posthumous Works of Thomas De Quincey, volume II, London: William Heinemann
2. (idiomatic) A particularly significant day; a day of personal or sectarian celebration.
   • Monday was a red letter day for her. She accomplished a lot and had fun doing it.
   • We saw losses for days in a row, but Black Tuesday was the worst red letter day of them all.

   Synonyms:

   day of days, red letter date