# Year - Calendar Year

Calendar Year

A calendar year is the time between two dates with the same name in a calendar. A half year (one half of a year) may run from January to June, or July to December.

No astronomical year has an integer number of days or lunar months, so any calendar that follows an astronomical year must have a system of intercalation such as leap years. Financial and scientific calculations often use a 365-day calendar to simplify daily rates.

In the Julian calendar, the average length of a year is 365.25 days. In a non-leap year, there are 365 days, in a leap year there are 366 days. A leap year occurs every four years.

The Gregorian calendar attempts to keep the vernal equinox on or soon before March 21, hence it follows the vernal equinox year. The average length of this calendar's year is 365.2425 days (as 97 out of 400 years are leap years); this is within one ppm of the current length of the mean tropical year (365.24219 days). It is estimated that, by the year 4000, the vernal equinox will fall back by one day in the Gregorian calendar, not because of this difference, but because of the slowing down of the Earth's rotation and the associated lengthening of the sidereal day.

The Revised Julian calendar, as used in some Eastern Orthodox Churches, also tries to synchronize with the tropical year. The average length of this calendar's year is 365.242222 days (as 218 out of 900 years are leap years). Gregorian and Revised Julian calendars will start to differ in 2800.

The Persian calendar, in use in Afghanistan and Iran, has its year begin on the day of the vernal equinox as determined by astronomical computation (for the time zone of Tehran), as opposed to using an algorithmic system of leap years.

### Other articles related to "calendar year, year, calendar, years":

Australian Masters
... the tournament is played late in the calendar year, in November or December, it formed part of the following year's European Tour schedule from 2006 through 2008 ... the European Tour's decision to realign its schedule with the calendar year for 2010, the 2009 event was the first to be part of the current calendar year's tour schedule ...
2006 Battery Directive - Recycling and Collection of Batteries
... rate' means, for a given Member State in a given calendar year, the percentage obtained by dividing the weight of waste portable batteries and accumulators collected in accordance with Article 8(1) of this ...
Calendar Year - Quarters
... The calendar year can be divided into 4 quarters, often abbreviated Q1, Q2, Q3 and Q4 First quarter from the beginning of January to the end of March Second quarter from the beginning of April to ...
List Of Myth Busters Episodes
... The show does not follow a typical calendar of on and off air periods ... MythBusters website lists episodes by calendar year ... sells DVD sets for "seasons", which sometimes follow the calendar year and sometimes do not ...
Presidential Nomination Process (US) - Procedure - Election Calendar
... and election process usually takes almost two years ... this process are as follows Spring of the previous calendar year – Candidates announce their intentions to run Summer to December of the previous calendar year – Primary and caucus debates January to June ...

### Famous quotes containing the words year and/or calendar:

As the Americans slaughter millions of turkeys every year for the celebration of their deliverance, the Indians, who should be celebrated as saviors, have long been slaughtered. There was even a time when a white man was paid a very decent price for every Indian scalp he could produce.
Friedrich Dürrenmatt (1921–1990)

To divide one’s life by years is of course to tumble into a trap set by our own arithmetic. The calendar consents to carry on its dull wall-existence by the arbitrary timetables we have drawn up in consultation with those permanent commuters, Earth and Sun. But we, unlike trees, need grow no annual rings.