Question

What name is given to a special day or happening, used variously over centuries to mark important days in a calendar, to mark capitals or rubrics in religious texts, or to wear particular clothing?

Answer 1

Red letter, or scarlet
Days of special significance were written in red in calendars found from ancient Rome, and many calendars still indicate special dates, festivals and holidays in red. In mediaeval (and later) religious manuscripts, initial capital letters, and text highlighted for emphasis, were written in red ink. Scarlet days, In UK universities, are when doctors may wear their scarlet full dress gowns, and in the English High Court are when judges wear their scarlet court robes at sittings of the Court of Law.