什么日子被叫做“red-letter day”?

Red-letter Day -Tomorrow is a red-letter day for the company; they celebrate a big anniversary. -The couple celebrated their red-letter day at cabin in the woods. -It's a red letter day for the country, everyone is celebrating. Meaning: A red-letter day is any day of special significance or opportunity. Origin: Its roots are in classical antiquity; for instance, important days are indicated in red in a calendar dating from the Roman Republic. In medieval manuscripts, initial capitals and highlighted words (known as rubrics) were written in red ink. ****** Other examples: 1. Before him, no one received a proper education in his family. Therefore, the day he went to study in the university has become a red-letter day for the family. 2. His girlfriend kept inventing and celebrating so many "red-letter days" until finally he got fed up and threatened to break up with her.