a red-letter day

red-letter day

A very important or significant day. My college graduation was a real red-letter day for my whole family.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

a red-letter day

A red-letter day is a day when something very important or exciting happens. Back in 1986 Jim had his first picture published in BBC Wildlife Magazine. `That was a real red-letter day for me!' he confesses. Note: In the past, important feast days and saints' days were printed in red in some calendars.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012

a red-ˈletter day

a very special day which is remembered because something important or good happened: Today was a red-letter day. We heard we had won a free trip to Japan.Religious holidays and other important dates used to be printed in red on calendars.
Farlex Partner Idioms Dictionary © Farlex 2017

red-letter day, a

A special occasion. The term comes from the practice of printing feast days and other special holy days in red on ecclesiastical calendars, from the fifteenth century on. Charles Lamb used the expression in describing Oxford during the long vacation: “The red-letter days now become, to all intents and purposes, dead-letter days” (Essays of Elia, 1823).
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
See also: