Lunar New Year is the beginning of a new year based on lunar calendars or, informally, lunisolar calendars. Lunar calendar years begin with a new moon and have a fixed number of lunar months, usually twelve. In contrast, a lunisolar calendar year has a variable number of lunar months so that, every few years, its start resynchronises with the solar year. The event is celebrated by numerous cultures in various ways at different dates. The determination of the first day of a new lunar year or lunisolar year varies by culture.