black letter day
Preserved but no longer current.
An unlucky day; one to be recalled with regret. m The Romans marked their unlucky days with a piece of black charcoal, and their lucky ones with white chalk, but the allusion here is to the old liturgical calendars in which the saints' days and festivals are distinguished by being printed in red.
Era: ca. 1898 (Victorian)
Sources & notes
Reproduced from Brewer’s Dictionary of Phrase and Fable (1898 edition, public domain; archive.org, retrieved 2026-07-31; OCR text, minor errors possible). Reflects the scholarship and attitudes of its era.
Common questions
What does “black letter day” mean?
An unlucky day; one to be recalled with regret. m The Romans marked their unlucky days with a piece of black charcoal, and their lucky ones with white chalk, but the allusion here is to the old liturgical calendars in which the saints' days and festivals are distinguished by being printed in red.
Is “black letter day” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.