red-letter

[ red-let-er ]

/ ˈrɛdˈlɛt ər /

marked by red letters, as festival days in the church calendar.

memorable; especially important or happy: a red-letter day in his life.

Words nearby red-letter

late Middle English word dating back to 1400–50

Turns out, after all, to be a red-letter day or, that is, a brown-liquid evening.
The Ridiculousness of Father's Day|P. J. O’Rourke|June 15, 2014|DAILY BEAST
When alluding, in after years, to this visit, Browning always spoke of it as one of the red-letter days of his life.
Life of Robert Browning|William Sharp
Love can always find some way to keep the red-letter days of its calendar.
The Little Colonel's Holidays|Annie Fellows Johnston
Sheep-shearing day continued the red-letter day on Nantucket well into the present century.
Nooks and Corners of the New England Coast|Samuel Adams Drake

January 24, 1848, was the red-letter day in California's history, and the news that transpired that day electrified the world.
Wealth of the World's Waste Places and Oceania |Jewett Castello Gilson
It was one of the red-letter days of my life, the day I owned a watch.
Life on the Stage|Clara Morris