The first day of the Gregorian calendar year — globally observed.
New Year's Day on January 1 marks the start of the Gregorian calendar year. While the date is secular, it has been a public holiday in most countries since the Gregorian calendar was widely adopted in the 16th-17th centuries. In some Christian traditions it is also the Feast of the Circumcision of Christ or the Solemnity of Mary, Mother of God.
Computed for Cachan (Europe/Paris) using local sunrise, sunset and astronomical positions.