[a] The astronomer's mean tropical year, which is averaged over equinoxes and solstices, is currently 365.24219 days, slightly shorter than the average length of the calendar year in most calendars.
The calendar year can be divided into four quarters,[3] often abbreviated as Q1, Q2, Q3, and Q4.
One in five to six years has a 53rd week which is usually appended to the last quarter.
In the Chinese calendar, the quarters are traditionally associated with the 4 seasons of the year: The calendar year can also be divided into quadrimesters (from French quadrimestre),[5] lasting for four months each.
They can also be called the early, middle, or late parts of the year.