Lunar New Year

Tết (, ), short for '''''' (; ), is the most important celebration in Vietnamese culture. Tết celebrates the arrival of spring, which is on the first day of the first Vietnamese lunisolar month, and usually falls between late January and 20 February in the Gregorian calendar.

January 1, a national holiday in Japan (the first day of the first month of the East Asian Lunar calendar prior to 1873)

Lunar New Year marks the beginning of a new year according to lunar calendars or, informally but commonly, to lunisolar calendars. Because a year of twelve lunar months is about 11 days shorter than a solar year, lunar cycle-based calendars may have strategies to take this fact into account. Pure lunar calendars have twelve lunar months invariantly and consequently their New Year is not fixed relative to the solar year; no adjustments are made. In contrast, most lunisolar calendars also have twelve lunar months, but every few years, a thirteenth "leap month" is added to resynchronise with the solar year. Consequently, neither type of calendar begins on a fixed date in the international Gregorian calendar.

first day of the year according to the Mongolian lunar calendar