New Year is the time or day currently at which a new calendar year and the total count increases by 1.
Other cultures observe their traditional or religious New Year's Day according to their own customs, due to the usage of a lunar calendar or a lunisolar calendar.
Chinese New Year the Islamic New Year, Tamil New Year (Puthandu are a few well-known examples. India, Nepal, and other countries also celebrate New Year on dates according to their own calendars that are movable in the Gregorian calendar.
During the Middle Ages in Western Europe, the Julian calendar was still in use, authorities moved New Year's Day corresponding to the locality, to one of several other days, including March 1, March 25, Easter etc.
Since then, many national civil calendars in the West and beyond have changed to using one fixed date for New Year's Day, January 1—when the Gregorian Calendar was adopted.
Happy new Year!