Lunar New Year is the first day of a secular, sacred, or other year whose months are coordinated by the cycles of the moon. The whole year may account to a purely lunar calendar, which is not coordinated to a solar calendar (and, thus, may progress or retrogress through the solar year by comparison to it, depending on whether the lunar calendar has more or fewer than 13 months); or the year may account to a lunisolar calendar, whose months coordinate to the cycles of the moon but whose length is periodically adjusted to keep it relatively in sync with the solar year - typically by adding an intercalary month, when needed.