The festival is not a day. It runs from New Year's Eve to the Lantern Festival on the fifteenth day, the first full moon of the year, and the intervening days have assigned characters, which relatives are visited on which day, when the god of wealth is welcomed, when it is unlucky to sweep.
The reunion dinner on the eve is the observance with the greatest social weight, and the travel it generates, the chunyun period, is the largest annual human migration in the world, measured in the billions of trips.
The red envelope given to children and unmarried adults, the red couplets on doorframes, the avoidance of certain words, the ban on sweeping in the first days lest fortune be swept out: these are widely observed regardless of religious belief, which is characteristic of the Chinese festival calendar. Much of the year's ritual apparatus operates as custom rather than as confessional practice.
The Nian monster story, a beast frightened away by red, noise and fire, said to explain the firecrackers and the colour, is often presented as ancient and appears to be relatively late in its current form, with no early textual basis. It is a good etiological tale of the kind that accumulates around long-established customs.
The official name in the People's Republic since 1912 is the Spring Festival, a republican-era coinage introduced when the Gregorian calendar was adopted for civil purposes and the term "new year" was reassigned to 1 January. The traditional calendar remains in official use for festivals and is published by the Purple Mountain Observatory.