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abstraction > mathematical concept > unit > time unit > year

year
subject			fact

year	has definition A period of time based on the revolution of the Earth around the Sun.
	is a kind of time unit
time unit	is a unit of time
unit	has historical origin
	represents

Kinds of year :

• anomalistic year (4 facts) - The interval between two successive perihelion passages of Earth., A period of time based on the revolution of the Earth around the Sun, where a year is defined as the mean interval between successive passages of the Earth through perihelion.
• Besselian year (2 facts) - The period of one complete revolution in right ascension of the fictitious mean sun, as defined by Newcomb. The beginning of a Besselian year, traditionally used as as standard epoch, is denoted by the suffix ".0". Since 1984 standard epochs have been defined by the Julian year rather that the Besselian year. For distinction, the beginning of the Besselian year is now identified by the prefix B (e.g., B1950.0).
• calendar year (3 facts) - is an approximation to the tropical year.
• eclipse year (3 facts) - The interval of time between two successive passages of the Sun through the same node of the Moon's orbit.
• Gaussian year (2 facts) - The period associated with Kepler's third law with a = 1.
• Julian year (3 facts) - A period served as the basis for the Julian calendar.
• sidereal year (2 facts) - A period of time based on the revolution of the Earth around the Sun, where a year is defined as the mean period of revolution with respect to the background stars.
• tropical year (4 facts) - The period of one complete revolution of the mean longitude of the sun with respect to the dynamical equinox. The tropical year is longer than the Besselian year by 0^s.148 T, where T is centuries from B1900.0., The interval of time between two successive vernal equinoxes.