Red letter day

A red letter day (sometimes hyphenated as red-letter day or called scarlet day in academia) is any day of special significance or opportunity Its roots are in classical antiquity; for instance, important days are indicated in red in a calendar dating from the Roman Republic (509–27 BC). 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. The practice did not originate, as it often assumed, from Medieval church calendars or a requirement that important holy days be marked in red from First Council of Nicaea in 325 AD, as has widely been claimed.