AskDefine | Define year

The Collaborative Dictionary

Sidereal \Si*de"re*al\, a. [L. sidereus, from sidus, sideris, a constellation, a star. Cf. Sideral, Consider, Desire.]
Relating to the stars; starry; astral; as, sidereal astronomy. [1913 Webster]
(Astron.) Measuring by the apparent motion of the stars; designated, marked out, or accompanied, by a return to the same position in respect to the stars; as, the sidereal revolution of a planet; a sidereal day. [1913 Webster] Sidereal clock, day, month, year. See under Clock, Day, etc. Sideral time, time as reckoned by sideral days, or, taking the sidereal day as the unit, the time elapsed since a transit of the vernal equinox, reckoned in parts of a sidereal day. This is, strictly, apparent sidereal time, mean sidereal time being reckoned from the transit, not of the true, but of the mean, equinoctial point. [1913 Webster]
Year \Year\, n. [OE. yer, yeer, [yogh]er, AS. ge['a]r; akin to OFries. i?r, g?r, D. jaar, OHG. j[=a]r, G. jahr, Icel. [=a]r, Dan. aar, Sw. [*a]r, Goth. j?r, Gr. ? a season of the year, springtime, a part of the day, an hour, ? a year, Zend y[=a]re year. [root]4,
Cf. Hour, Yore.] [1913 Webster]
The time of the apparent revolution of the sun trough the ecliptic; the period occupied by the earth in making its revolution around the sun, called the astronomical year; also, a period more or less nearly agreeing with this, adopted by various nations as a measure of time, and called the civil year; as, the common lunar year of 354 days, still in use among the Mohammedans; the year of 360 days, etc. In common usage, the year consists of 365 days, and every fourth year (called bissextile, or leap year) of 366 days, a day being added to February on that year, on account of the excess above 365 days (see Bissextile). [1913 Webster] Of twenty year of age he was, I guess. --Chaucer. [1913 Webster] Note: The civil, or legal, year, in England, formerly commenced on the 25th of March. This practice continued throughout the British dominions till the year
[1913 Webster]
The time in which any planet completes a revolution about the sun; as, the year of Jupiter or of Saturn. [1913 Webster]
pl. Age, or old age; as, a man in years. --Shak. [1913 Webster] Anomalistic year, the time of the earth's revolution from perihelion to perihelion again, which is 365 days, 6 hours, 13 minutes, and 48 seconds. A year's mind (Eccl.), a commemoration of a deceased person, as by a Mass, a year after his death. Cf. A month's mind, under Month. Bissextile year. See Bissextile. Canicular year. See under Canicular. Civil year, the year adopted by any nation for the computation of time. Common lunar year, the period of 12 lunar months, or 354 days. Common year, each year of 365 days, as distinguished from leap year. Embolismic year, or Intercalary lunar year, the period of 13 lunar months, or 384 days. Fiscal year (Com.), the year by which accounts are reckoned, or the year between one annual time of settlement, or balancing of accounts, and another. Great year. See Platonic year, under Platonic. Gregorian year, Julian year. See under Gregorian, and Julian. Leap year. See Leap year, in the Vocabulary. Lunar astronomical year, the period of 12 lunar synodical months, or 354 days, 8 hours, 48 minutes, 36 seconds. Lunisolar year. See under Lunisolar. Periodical year. See Anomalistic year, above. Platonic year, Sabbatical year. See under Platonic, and Sabbatical. Sidereal year, the time in which the sun, departing from any fixed star, returns to the same. This is 365 days, 6 hours, 9 minutes, and 9.3 seconds. Tropical year. See under Tropical. Year and a day (O. Eng. Law), a time to be allowed for an act or an event, in order that an entire year might be secured beyond all question. --Abbott. Year of grace, any year of the Christian era; Anno Domini; A. D. or a. d. [1913 Webster] year 2000 bug

Word Net



1 a period of time containing 365 (or 366) days; "she is 4 years old"; "in the year 1920" [syn: twelvemonth, yr]
2 a period of time occupying a regular part of a calendar year that is used for some particular activity; "a school year"
3 the period of time that it takes for a planet (as, e.g., Earth or Mars) to make a complete revolution around the sun; "a Martian year takes 687 of our days"
4 a body of students who graduate together; "the class of '97"; "she was in my year at Hoehandle High" [syn: class]

Moby Thesaurus

abundant year, academic year, annum, bissextile year, calendar month, calendar year, century, common year, day, decade, decennary, decennium, defective year, fiscal year, fortnight, hour, leap year, lunar month, lunar year, lunation, luster, lustrum, man-hour, microsecond, millennium, millisecond, minute, moment, month, moon, quarter, quinquennium, regular year, second, semester, session, sidereal year, solar year, sun, term, trimester, twelvemonth, week, weekday



Old English ġēar.


  • (RP) /jiə/, /jɜː/, /ji@/, /j3:/
  • (US) , /jiɹ/, /jir/
  • Rhymes: -ɪə(r)


  1. The time it takes the Earth to complete one revolution of the Sun (between 365.24 and 365.26 days depending on the point of reference).
    We moved to this town a year ago.
    I quit smoking exactly one year ago.
  2. In the context of "by extension": The time it takes for any planetary body to make one revolution around another body.
    Mars goes around the sun once in a Martian year, or 1.88 Earth years.
  3. A period between set dates that mark a year, from January 1 to December 31 by the Gregorian calendar.
    A normal year has 365 full days, but there are 366 days in a leap year.
    I was born in the year 1950.
    This Chinese year is the year of the Rooster.
  4. A scheduled part of a calendar year spent in a specific activity.
    During this school year I have to get up at 6:30 to catch the bus.
  5. A Julian year, exactly 365.25 days, represented by "a".
  6. A level or grade in school or college.
    Every second-year student must select an area of specialization.
    The exams in year 12 at high school are the most difficult.


time it takes for the Earth to complete one revolution of the Sun
time it takes for any planetary body to make one revolution around another body
  • Dutch: jaar
  • Estonian: aasta
  • Finnish: vuosi, kiertoaika
  • Greek: χρόνος (chrónos), έτος (étos)
  • Italian: anno
  • Kurdish:
    Sorani: ساڵ
  • Ladino: anyada
  • Maltese: sena
  • Russian: год
  • Spanish: año
a period between set dates that mark a year
a scheduled part of a calendar year spent in a specific activity
  • Dutch: jaar
  • Finnish: vuosi
  • Greek: χρόνος (chrónos), έτος (étos)
  • Italian: anno
  • Kurdish:
    Sorani: ساڵ
  • Russian: год
  • Telugu: సంవత్సరము (samvatsaramu)
a Julian year
  • Dutch: jaar
  • Finnish: vuosi
  • Italian: anno
  • Kurdish:
    Sorani: ساڵ
  • Ladino: anyada
  • Russian: год
  • Spanish: año
a level or grade at school or college
  • Chinese: 年級 (nián jí)
  • Dutch: jaar
  • Ewe: eƒe
  • Finnish: luokka
  • Italian: anno
  • Kurdish:
    Sorani: ساڵ, پۆل
  • Maltese: sena
  • Russian: класс (klass) at school, курс (kurs) at college or university
  • Spanish: año, grado
A year (from Old English gēr) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. By extension, this can be applied to any planet: for example, a "Martian year" is the time in which Mars completes its own orbit.


West Saxon gear, Anglian gēr continues Proto-Germanic *jǣram (*jē2ram). Cognates are Old High German jar, Old Norse ár and Gothic jer, all from a PIE *yērom "year, season". Cognates outside of Germanic are Avestan yare "year", Greek "year, season, period of time" (whence "hour"), Old Church Slavonic jaru and Latin hornus "of this year".
Latin annum is from a base *at-no-. Both *yē-ro- and *at-no- are based on verbal roots expressing movement, *at- and *ey- respectively, both meaning "to go" generally. Latin annum has a cognate in Gothic aþnam "year". The Greek word for "year", , is cognate to Latin vetus "old", from PIE *wetus- "year" , also preserved in this meaning in Sanskrit "yearling (calf)".

Calendar year

A calendar year is the time between two dates with the same name in a calendar.
The Gregorian calendar attempts to keep the vernal equinox on or close to March 21; hence it follows the vernal equinox year. The average length of this calendar's year is 365.2425 days (which can be thought of as 97 out of 400 years being leap years) whereas the vernal equinox year is 365.2424 days.
Among solar calendars in wide use today, the Persian calendar is one of the most precise. Rather than being based on numerical rules, the Persian year begins on the day (for the time zone of Tehran) on which the vernal equinox actually falls, as determined by precise astronomical computations.
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.
In the Julian calendar, the average length of a year was 365.25 days. (This is still used as a convenient time unit in astronomy as shown below.) In a non-leap year, there are 365 days, in a leap year there are 366 days. A leap year occurs every 4 years.

Seasonal year

A seasonal year is the time between successive recurrences of a seasonal event such as the flooding of a river, the migration of a species of bird, the flowering of a species of plant, the first frost, or the first scheduled game of a certain sport. All of these events can have wide variations of more than a month from year to year.

Fiscal year

A fiscal year is a 12-month period used for calculating annual financial statements in businesses and other organizations. In many jurisdictions, regulations regarding accounting require such reports once per twelve months, but do not require that the twelve months constitute a calendar year. For example, the federal government of the U.S. has a fiscal year that starts on October 1st instead of January 1st. In Australia the financial year runs from July 1st. In Canada, from April 1st.

Academic year

An academic year refers to the annual period during which a student attends school, college or university.
The school year can be divided up in various ways, two of which are most common in North American educational systems.
  • Many schools divide the academic year into three roughly equal-length trimesters (called terms in the UK), more or less coinciding with autumn, winter, and spring. At some, a somewhat shortened summer session, not usually considered part of the regular academic year, is attended by students on a voluntary or elective basis.
  • Other schools break the year into two main semesters, a first (typically August through December) and a second (January through May). Each of these main semesters may be split in half by mid-term exams, and each of the halves is referred to as a quarter (or term in some countries). There may also be an elective summer session, and/or a short January session.
  • Some other places, such in the United States, have four 'marking periods.' The school year startes in early September and ends in Mid-June. There are 180 days in all of school(excluding weekends and breaks.) Most commonly, there is a summer break, last two weeks of June to the beginning of September.

Astronomical years

Julian year

The Julian year, as used in astronomy and other sciences, is a time unit defined as exactly 365.25 days. This is the normal meaning of the unit "year" (symbol "a" from the Latin annus, annata) used in various scientific contexts. The Julian century of 36,525 days and the Julian millennium of 365,250 days are used in astronomical calculations. Fundamentally, expressing a time interval in Julian years is a way to precisely specify how many days (not how many "real" years), for long time intervals where stating the number of days would be unwieldy and unintuitive. By convention, the Julian year is used in the computation of the distance covered by a light-year.

Sidereal, tropical, and anomalistic years

The relations among these are considered more fully in Precession (astronomy).
Each of these three years can be loosely called an 'astronomical year'.
The sidereal year is the time taken for the Earth to complete one revolution of its orbit, as measured against a fixed frame of reference (such as the fixed stars, Latin sidera, singular sidus). Its duration in SI days of 86,400 SI seconds each is on average:
365.256 363 051 days (365 d 6 h 9 min 9.7676 s) (at the epoch J2000.0 = 2000 January 1 12:00:00 TT).
The tropical year is the time taken for the Earth to complete one revolution with respect to the framework provided by the intersection of the ecliptic (the plane of the orbit of the Earth) and the plane of the equator (the plane perpendicular to the rotation axis of the Earth). The exact length of a tropical year slightly depends on the chosen starting point: for example the vernal equinox year is the time between successive vernal equinoxes. The mean tropical year (averaged over all ecliptic points) is:
365.242 189 67 days (365 d 5 h 48 min 45 s) (at the epoch J2000.0).
The tropical year is shorter than the sidereal year because of the precession of the equinoxes.
The anomalistic year is the time taken for the Earth to complete one revolution with respect to its apsides. The orbit of the Earth is elliptical; the extreme points, called apsides, are the perihelion, where the Earth is closest to the Sun (January 3 in 2008), and the aphelion, where the Earth is farthest from the Sun (July 4 in 2008). The anomalistic year is usually defined as the time between two successive perihelion passages. Its average duration is:
365.259 635 864 days (365 d 6 h 13 min 52 s) (at the epoch J2000.0).
The anomalistic year is slightly longer than the sidereal year because of the precession of the apsides (or anomalistic precession).

Draconic year

The draconic year, draconitic year, eclipse year, or ecliptic year is the time taken for the Sun (as seen from the Earth) to complete one revolution with respect to the same lunar node (a point where the Moon's orbit intersects the ecliptic). This period is associated with eclipses: these occur only when both the Sun and the Moon are near these nodes; so eclipses occur within about a month of every half eclipse year. Hence there are two eclipse seasons every eclipse year. The average duration of the eclipse year is:
346.620 075 883 days (346 d 14 h 52 min 54 s) (at the epoch J2000.0).
This term is sometimes erroneously used to designate the draconic or nodal period of lunar precession, that is the time it takes for a complete revolution of the Moon's ascending node around the ecliptic: 18.612 815 932 Julian years (6798.331 019 days; at the epoch J2000.0).

Full moon cycle

The full moon cycle is the time for the Sun (as seen from the Earth) to complete one revolution with respect to the perigee of the Moon's orbit. This period is associated with the apparent size of the full moon, and also with the varying duration of the synodic month. The duration of one full moon cycle is:
411.784 430 29 days (411 d 18 h 49 min 34 s) (at the epoch J2000.0).

Lunar year

The lunar year comprises twelve full cycles of the phases of the Moon, as seen from Earth. It has a duration of approximately 354.37 days.

Heliacal year

A heliacal year is the interval between the heliacal risings of a star. It differs from the sidereal year for stars away from the ecliptic due mainly to the precession of the equinoxes (To visualise: the constellation Crux which rose and set as seen from the Mediterranean in ancient Greek times, is never above the horizon in current times.)

Sothic year

The Sothic year is the interval between heliacal risings of the star Sirius. Its duration is very close to the mean Julian year of 365.25 days.

Gaussian year

The Gaussian year is the sidereal year for a planet of negligible mass (relative to the Sun) and unperturbed by other planets that is governed by the Gaussian gravitational constant. Such a planet would be slightly closer to the Sun than Earth's mean distance. Its length is:
365.256 898 3 days (365 d 6 h 9 min 56 s).

Besselian year

The Besselian year is a tropical year that starts when the fictitious mean Sun reaches an ecliptic longitude of 280°. This is currently on or close to 1 January. It is named after the 19th century German astronomer and mathematician Friedrich Bessel. An approximate formula to compute the current time in Besselian years from the Julian day is:
B = 2,000 + (JD - 2,451,544.53) /365.242189

Great year

The Great year, Platonic year, or Equinoctial cycle corresponds to a complete revolution of the equinoxes around the ecliptic. Its length is about 25,700 years, and cannot be determined precisely as the precession speed is variable.

Galactic year

The Galactic year is the time it takes Earth's solar system to revolve once around the galactic center. It comprises roughly 226 million Earth years.

Variation in the length of the year and the day

The exact length of an astronomical year changes over time. The main sources of this change are:
  • The precession of the equinoxes changes the position of astronomical events with respect to the apsides of Earth's orbit. An event moving toward perihelion recurs with a decreasing period from year to year; an event moving toward aphelion recurs with an increasing period from year to year. But this effect don't change the average value of the length of the year.
  • The gravitational influence of the Moon and planets changes the motion of the Earth from a steady orbit around the Sun. The Earth orbit varies by a chaotic way, but in a interval quite more reduced than the orbits of the nearest planets.
  • Tidal drag between the Earth and the Moon and Sun increases the length of the day and of the month (by transferring angular momentum from the rotation of the Earth to the revolution of the Moon); since the apparent mean solar day is the unit with which we measure the length of the year in civil life, the length of the year appears to change. Tidal drag in turn depends on factors such as post-glacial rebound and sea level rise.
  • Changes in the effective mass of the Sun, caused by solar wind and radiation of energy generated by nuclear fusion and radiated by its surface, will affect the Earth's orbital period over a long time (approximately an extra 1.25 microsecond per year).

Summary of various kinds of year

  • 346.62 days - a draconitic year in some septenary calendars.
  • 353, 354 or 355 days — the lengths of common years in some lunisolar calendars.
  • 354.37 days/12 lunar months - the average length of a year in lunar calendars.
  • 365 days — a common year in many solar calendars.
  • 365.24219 days — a mean tropical year near the year 2000.
  • 365.2424 days — a vernal equinox year.
  • 365.2425 days — the average length of a year in the Gregorian calendar.
  • 365.25 days — the average length of a year in the Julian calendar.
  • 365.2564 days — a sidereal year.
  • 366 days — a leap year in many solar calendars.
  • 383, 384 or 385 days — the lengths of leap years in some lunisolar calendars.
  • 383.9 days/13 lunar months - a leap year in some lunisolar calendars.
An average Gregorian year is 365.2425 days = 52.1775 weeks, 8,765.82 hours = 525,949.2 minutes = 31,556,952 seconds (mean solar, not SI). A common year is 365 days = 8,760 hours = 525,600 minutes = 31,536,000 seconds. A leap year is 366 days = 8,784 hours = 527,040 minutes = 31,622,400 seconds. The 400-year cycle of the Gregorian calendar has 146,097 days and hence exactly 20,871 weeks. See also numerical facts about the Gregorian calendar.

Numeration or designation of year numbers

A calendar era is used to assign a number to individual years, using a reference point in the past as the beginning of the era. In many countries, the most common era is from the estimated date of the birth of Jesus Christ; dates in this era are designated anno Domini ("in the year of the Lord", abbreviated A.D.) or, more neutrally, C.E. (common era). Other eras are also used to enumerate the years in different cultural, religious or scientific contexts.

Notes and References

See also

year in Afrikaans: Jaar
year in Tosk Albanian: Jahr
year in Arabic: عام
year in Aragonese: Año
year in Official Aramaic (700-300 BCE): ܫܢܬܐ (ܙܒܢܐ)
year in Asturian: Añu
year in Aymara: Mara
year in Min Nan: Nî
year in Belarusian: Год
year in Belarusian (Tarashkevitsa): Год
year in Bosnian: Godina
year in Breton: Bloaz
year in Bulgarian: Година
year in Catalan: Any
year in Chuvash: Çул
year in Cebuano: Tuig
year in Czech: Rok
year in Welsh: Blwyddyn
year in Danish: År
year in German: Jahr
year in Estonian: Aasta
year in Modern Greek (1453-): Έτος
year in Emiliano-Romagnolo: Ân
year in Erzya: Ие
year in Spanish: Año
year in Esperanto: Jaro
year in Basque: Urte
year in Persian: سال
year in French: Année (calendrier)
year in Western Frisian: Jier
year in Friulian: An
year in Irish: Bliain
year in Gan Chinese: 年
year in Scottish Gaelic: Bliadhna
year in Galician: Ano
year in Korean: 년
year in Croatian: Godina
year in Ido: Yaro
year in Indonesian: Tahun
year in Interlingua (International Auxiliary Language Association): Anno
year in Inuktitut: ᐅᑭᐅᖅ/ukuiq
year in Ossetian: Аз
year in Icelandic: Ár
year in Italian: Anno
year in Hebrew: שנה
year in Javanese: Taun
year in Georgian: წელი
year in Swahili (macrolanguage): Mwaka
year in Haitian: Lane
year in Kurdish: Sal
year in Ladino: Anyo
year in Lao: ປີ
year in Latin: Annus
year in Latvian: Gads
year in Luxembourgish: Joer
year in Lithuanian: Metai
year in Limburgan: Jaor
year in Hungarian: Év
year in Maori: Tau
year in Malay (macrolanguage): Tahun
year in Mongolian: Жил
year in Dutch: Jaar
year in Japanese: 年
year in Norwegian: År
year in Norwegian Nynorsk: År
year in Narom: Aun
year in Occitan (post 1500): Annada
year in Uzbek: Yil
year in Low German: Johr
year in Polish: Rok
year in Portuguese: Ano
year in Romanian: An
year in Vlax Romani: Bersh
year in Quechua: Wata
year in Russian: Год
year in Albanian: Viti
year in Sicilian: Annu
year in Simple English: Year
year in Slovak: Rok
year in Slovenian: Leto
year in Somali: Sanad
year in Serbian: Година
year in Serbo-Croatian: Godina
year in Sundanese: Taun
year in Finnish: Vuosi
year in Swedish: År
year in Tagalog: Taon
year in Tamil: ஆண்டு
year in Telugu: సంవత్సరము
year in Thai: ปี
year in Tok Pisin: Yia
year in Turkish: Yıl
year in Ukrainian: Рік
year in Urdu: سال
year in Võro: Aastak
year in Yiddish: יאר
year in Yoruba: Ọdún
year in Contenese: 年
year in Samogitian: Metā
year in Chinese: 年
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