元旦是指每年的1月1日，是世界上许多国家和地区的公共节日。它的由来可以追溯到公元前45年罗马共和国定下的日历，将1月1日定为新年第一天。这个传统一直延续到现代，成为了全球范围内的重要节日。 New Year's Day, also known as January 1st, is a public holiday in many countries and regions around the world. Its origin can be traced back to the calendar established by the Roman Republic in 45 BC, which set January 1st as the first day of the new year. This tradition has continued to the present day, becoming an important global holiday.