"Years" redirects here. For other uses, see Years (disambiguation).
"12 months" redirects here. For other uses, see The Twelve Months (disambiguation).
An animation of the inner Solar
System planets' orbit around the Sun. The duration of the year is the time taken to go around the
Sun.
A year is a unit of time based on how long it takes the Earth to orbit the Sun.[1] In scientific use,
the tropical year (approximately 365 solar days, 5 hours, 48 minutes, 45 seconds) and the sidereal
year (about 20 minutes longer) are more exact. The modern calendar year, as reckoned according to
the Gregorian calendar, approximates the tropical year by using a system of leap years.
The term 'year' is also used to indicate other periods of roughly similar duration, such as the lunar
year (a roughly 354-day cycle of twelve of the Moon's phases – see lunar calendar), as well as
periods loosely associated with the calendar or astronomical year, such as the seasonal year,
the fiscal year, the academic year, etc.
Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by changes
in weather, the hours of daylight, and, consequently, vegetation and soil fertility.
In temperate and subpolar regions around the planet, four seasons are generally
recognized: spring, summer, autumn, and winter. In tropical and subtropical regions, several
geographical sectors do not present defined seasons; but in the seasonal tropics, the
annual wet and dry seasons are recognized and tracked.
By extension, the term 'year' can also be applied to the time taken for the orbit of any astronomical
object around its primary – for example the Martian year of roughly 1.88 Earth years.
The term can also be used in reference to any long period or cycle, such as the Great Year.[2]
Calendar year
A calendar year is an approximation of the number of days of the Earth's orbital period, as counted in
a given calendar. The Gregorian calendar, or modern calendar, presents its calendar year to be either
a common year of 365 days or a leap year of 366 days, as do the Julian calendars. For the Gregorian
calendar, the average length of the calendar year (the mean year) across the complete leap cycle of
400 years is 365.2425 days (97 out of 400 years are leap years).[3]
Abbreviation
In English, the unit of time for year is commonly abbreviated as "y" or "yr". The symbol "a"
(for Latin: annus, year) is sometimes used in scientific literature, though its exact duration may be
inconsistent.[citation needed]
Etymology
English year (via West Saxon ġēar (/jɛar/), Anglian ġēr) continues Proto-Germanic *jǣran (*jē₁ran).
Cognates are German Jahr, Old High German jār, Old Norse ár and Gothic jer, from the Proto-Indo-
European noun *yeh₁r-om "year, season". Cognates also descended from the same Proto-Indo-
European noun (with variation in suffix ablaut) are Avestan yārǝ "year", Greek ὥρα (hṓra) "year,
season, period of time" (whence "hour"), Old Church Slavonic jarŭ, and Latin hornus "of this year".
[citation needed]
Latin annus (a 2nd declension masculine noun; annum is the accusative
singular; annī is genitive singular and nominative plural; annō the dative and ablative singular) is
from a PIE noun *h₂et-no-, which also yielded Gothic aþn "year" (only the dative plural aþnam is
attested).
Although most languages treat the word as thematic *yeh₁r-o-, there is evidence for an original
derivation with an *-r/n suffix, *yeh₁-ro-. Both Indo-European words for year, *yeh₁-ro- and *h₂et-no-,
would then be derived from verbal roots meaning "to go, move", *h₁ey- and *h₂et-, respectively
(compare Vedic Sanskrit éti "goes", atasi "thou goest, wanderest"). A number of English words are
derived from Latin annus, such as annual, annuity, anniversary, etc.; per annum means "each
year", annō Dominī means "in the year of the Lord".
The Greek word for "year", ἔτος, is cognate with Latin vetus "old", from the PIE word *wetos- "year",
also preserved in this meaning in Sanskrit vat-sa-ras "year" and vat-sa- "yearling (calf)", the latter
also reflected in Latin vitulus "bull calf", English wether "ram" (Old English weðer,
Gothic wiþrus "lamb").
In some languages, it is common to count years by referencing to one season, as in "summers", or
"winters", or "harvests". Examples include Chinese 年 "year", originally 秂, an ideographic compound
of a person carrying a bundle of wheat denoting "harvest". Slavic besides godŭ "time period; year"
uses lěto "summer; year".
