A red letter day (sometimes hyphenated as red-letter day or called scarlet day in academia) is any day of special significance.
Its roots are in classical antiquity. For instance, important days are indicated in red in a calendar dating from the Roman Republic (509–27 BCE). In medieval manuscripts, initial capitals and highlighted words (known as rubrics) were written in red ink. The practice was continued after the invention of the printing press, including in Catholic liturgical books. Many calendars still indicate special dates and holidays in red instead of black.
William Caxton, referred to it in The boke of Eneydos, translated and printed in 1490:
“We wryte yet in oure kalenders the hyghe festes wyth rede lettres of coloure of purpre.”
The term came into wider use in 1549 when the first Book of Common Prayer included a calendar with holy days marked in red ink; for example, Annunciation (Lady Day), 25th March, was designated in the book as a red-letter day.
In America, the term was used in the diary of Sarah Knight: The journals of Madam Knight, and Rev. Mr. Buckingham, which was written in 1704 and 1710, and published in American Speech in 1940.
In England, on red letter days, judges of the English High Court (Queen’s Bench Division) wear, at sittings of the Court of Law, their scarlet robes. Also in the UK, other civil dates have been added to the original religious dates. These include anniversaries of the Monarch’s birthday, official birthday, accession and coronation. In the universities of the UK, scarlet days are when doctors may wear their scarlet ‘festal’ or full dress gowns instead of their undress (‘black’) gown.
In Norway, Sweden, Denmark, South Korea and some Latin American countries, a public holiday is sometimes referred to as “red day,” as it is printed in red in calendars.
Here are some lines from the song lyrics of “A red letter day” by the Pet Shop Boys:
You can sneer or disappear
behind a veneer of self-contro
but for all of those
who don’t fit it
who follow their instincts
and are told they sin
this is a prayer for
a different way
All I want is what you want
I’m always waiting for a red letter day
All days are red letter days in the rain forest. But I guess I’d have to admit to being somewhat prejudiced!