Which holiday marks the first day of the Gregorian calendar year on January 1?

New Year's Day is the holiday that marks the first day of the Gregorian calendar year on January 1.

The Gregorian calendar, introduced by Pope Gregory XIII in 1582, retained January 1 as the beginning of the civil year in the Roman calendar tradition. Adoption happened gradually, so countries did not all change calendars at the same time. Today, January 1 is the official new-year date in most countries using the Gregorian calendar.

New Year's Day follows New Year's Eve, the final evening of the old calendar year. Many communities hold parades, religious services, concerts, family meals, or public ceremonies on January 1. The date is also a public holiday in numerous countries.

Not every culture begins its traditional or religious year on January 1. Lunar, lunisolar, and other calendars have different new-year dates, including Lunar New Year and Rosh Hashanah. The answer therefore refers specifically to the Gregorian civil calendar.