New Year's Day is the first day of a year. The term also refers to the celebrations of this first day of the year. Like any anniversary date of a given calendar, New Year's Day may seem mobile with regard to a calendar operating according to another logic. For example, the New Year of the Chinese calendar (luni-solar) appears as a moving date in the Gregorian calendar (solar calendar). The celebration of the New Year corresponds to the annual renewal of the primitive cosmogony and the cosmogony of origins, found in all primitive civilizations, and allows the fullness of the original world to be found again.

In temperate countries

Although New Year's Day rarely falls on the same date from one calendar to another, there is a relative concordance between countries. Indeed, the disappearance of vegetation during the winter and its rebirth in the spring fueled the widespread myth of the cyclical rebirth of the year. It is therefore not surprising that a large number of New Year's Day are celebrated between the winter solstice and the spring equinox.

In tropical countries

However, this is by no means universal, especially in tropical countries, where the cycle of seasons is much less tangible. One example is ancient Egypt, which, although using a solar calendar, celebrates the new year with the annual arrival of the Nile Lake. This flood is due to rains far upstream in the highlands, its date is entirely dependent on weather phenomena. However, it usually occurs at the same time.