New Year's Day is observed on January 1, the first day of the year on the modern Gregorian calendar as well as the Julian calendar used in the Roman Empire since 45 BC. Romans originally dedicated New Year's Day to Janus, the god of gates, doors, and beginnings for whom the first month of the year (January) is named. Later, as a date in the Gregorian calendar of Christendom, New Year's Day liturgically marked the Feast of the Circumcision of Christ, and is still observed as such in the Anglican Church and Lutheran Church. In present day, with most countries now using the Gregorian calendar as their de facto calendar, New Year's Day is probably the world's most celebrated public holiday, often observed with fireworks at the stroke of midnight as the new year starts in each time zone.
- New Year's Day on Wikipedia