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. In Physics, an orbit is the gravitationally curved path of one object around a point or another body for example the gravitational orbit of a planet around a star EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The Sun (Sol is the Star at the center of the Solar System. By extension, this can be applied to any planet: for example, a "Martian year" is the time in which Mars completes its own orbit. A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is

## Etymology

Further information: Jēran and annum

West Saxon gear, Anglian gēr continues Proto-Germanic *jǣram (*jē2ram). Annum is one form of the Latin noun meaning Year, not a form normally used for derivatives in modern languages the accusative singular West Saxon redirects here For other meanings of Wessex or West Saxon see Wessex (disambiguation. Anglian is a cover term used to refer to two Dialects of Old English, namely the Northumbrian and Mercian dialects Proto-Germanic, or Common Germanic, is the hypothetical common ancestor ( Proto-language) of all the Germanic languages such as modern English Eiwaz or Eihaz (reconstructed *īhaz / *ēhaz or *īwaz / *ēwaz) was a Proto-Germanic word for " yew " Cognates are Old High German jar, Old Norse ár and Gothic jer, all from a PIE *yērom "year, season". Old Norse is the North Germanic language that was spoken by inhabitants of Scandinavia and inhabitants of their overseas settlements during the Viking Age Gothic is an extinct Germanic language that was spoken by the Goths. Cognates outside of Germanic are Avestan yare "year", Greek ὥρα "year, season, period of time" (whence "hour"), Old Church Slavonic jaru and Latin hornus "of this year". Avestan is an Eastern Old Iranian language that was used to compose the sacred hymns and canon of the Zoroastrian Avesta. The Ancient Greek language is the historical stage in the development of the Hellenic language family spanning the Archaic (c The hour (symbol h) is a unit of Time. It is not an SI unit but is accepted for use with the SI to make sure old Cyrillic letters are displayed properly (For example instead of just Ѣ write Ѣ Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome.

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", ἔτος, is cognate to Latin vetus "old", from PIE *wetus- "year" , also preserved in this meaning in Sanskrit vat-sa- "yearling (calf)". Sanskrit (sa संस्कृता वाक् saṃskṛtā vāk, for short sa संस्कृतम् saṃskṛtam) is a historical

## Calendar year

A calendar year is the time between two dates with the same name in a calendar. According to the Gregorian calendar, the calendar year begins on January 1 and ends on December 31. The word Calendar consist of two words 1 Cal ( in Pashto means Year in Hindi and Persian is Sal- also means Year

The Gregorian calendar attempts to keep the vernal equinox on or close to March 21; hence it follows the vernal equinox year. The Gregorian calendar is the most widely used Calendar in the world today An equinox is the event of the Sun passing over the Earth's equator in its annual cycle Events 630 - Byzantine emperor Heraclius restores the True Cross to Jerusalem. A tropical year (also known as a solar year) is the length of time that the Sun takes to return to the same position in the cycle of seasons as seen from Earth 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. The Iranian calendar or Solar Hejri (تقویم هجری شمسی؛ سالنمای هجری خورشیدی Taqwim Hejri Shamsi Salanmay Hejri Khurshidi) is an astronomical 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. Tehran (or Teheran) ( Persian: تهران Tehrān) is the capital and largest City of Iran, and the administrative center of

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. Intercalation is the insertion of a leap day week or month into some calendar years to make the calendar follow the seasons or moon phases A leap year (or intercalary year) is a year containing one or more extra days (or in the case of Lunisolar calendars an extra month in order to keep the

In the Julian calendar, the average length of a year was 365. The Julian calendar, a reform of the Roman calendar, was introduced by Julius Caesar in 46 BC and came into force in 45 BC (709 Ab urbe condita 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. The 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 or the flowering of a species A season is one of the major divisions of the Year, generally based on yearly periodic changes in Weather. All of these events can have wide variations of more than a month from year to year. The month is a unit of Time, used with Calendars which is approximately as long as some natural period related to the motion of the Moon;

## Fiscal year

A fiscal year is a 12-month period used for calculating annual financial statements in businesses and other organizations. A fiscal year (or financial year, or sometimes budget year) is a period used for calculating annual ("yearly" Financial statements in Businesses 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. For a topic outline on this subject see List of basic Australia topics. In Canada, from April 1st. Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page

An academic year refers to the annual period during which a student attends school, college or university. An academic term is a division of an academic year the time during which a School, College or University holds classes

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. In Astronomy, a Julian year (symbol a) is a unit of measurement of Time defined 25 days. This is the normal meaning of the unit "year" (symbol "a" from the Latin annus, annata) used in various scientific contexts. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. 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. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by

### Sidereal, tropical, and anomalistic years

The relations among these are considered more fully in Precession (astronomy). In Astronomy, Precession refers to the movement of the rotational axis of a body such as a planet with respect to Inertial space.

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). The sidereal year is the time taken for the Sun to return to the same position with respect to the Stars of the Celestial sphere. 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). In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. Terrestrial Time (TT is the modern astronomical standard for the passage of time on the surface of the Earth (for civil purposes Coordinated Universal

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). A tropical year (also known as a solar year) is the length of time that the Sun takes to return to the same position in the cycle of seasons as seen from Earth The ecliptic is the apparent path that the Sun traces out in the sky during the year The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the 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. In Astronomy, Precession refers to the movement of the rotational axis of a body such as a planet with respect to Inertial space.

The anomalistic year is the time taken for the Earth to complete one revolution with respect to its apsides. In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from 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). In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from Events 1431 - Joan of Arc is handed over to the Bishop Pierre Cauchon. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from Events 836 - Pactum Sicardi, peace between the Principality of Benevento and the Duchy of Naples 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). In Astronomy, Precession refers to the movement of the rotational axis of a body such as a planet with respect to Inertial space.

### 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). The lunar nodes are the Orbital nodes of the Moon, that is the points where the orbit of the Moon crosses the Ecliptic (which is the apparent 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. An eclipse is an astronomical event that occurs when one Celestial object moves into the shadow of another 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. There are two important Precessional motions in the Orbit of the Moon. 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. The full moon cycle is a cycle of about 14 Lunations over which Full moons vary in apparent size and age (time since New moon) This period is associated with the apparent size of the full moon, and also with the varying duration of the synodic month. Full moon is a Lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. The month is a unit of Time, used with Calendars which is approximately as long as some natural period related to the motion of the Moon; 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. A lunar calendar is a Calendar that is based on cycles of the Moon phase. It has a duration of approximately 354. 37 days.

### Heliacal year

A heliacal year is the interval between the heliacal risings of a star. The heliacal rising of a Star (or other body such as the Moon, a Planet or a Constellation) occurs when it first becomes visible above the eastern 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. The sidereal year is the time taken for the Sun to return to the same position with respect to the Stars of the Celestial sphere. The ecliptic is the apparent path that the Sun traces out in the sky during the year In Astronomy, Precession refers to the movement of the rotational axis of a body such as a planet with respect to Inertial space. CRUX is a lightweight I686 -optimized Linux distribution targeted at experienced Linux users The Ancient Greek language is the historical stage in the development of the Hellenic language family spanning the Archaic (c )

### Sothic year

The Sothic year is the interval between heliacal risings of the star Sirius. The Sothic cycle or Canicular period is a period of 1461 Ancient Egyptian years (of 365 days each or 1460 Julian years (averaging 365 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. A Gaussian year is defined as 3652568983 Days It was adopted by Carl Friedrich Gauss as the length of the Sidereal year in his studies of the dynamics Carl Friedrich Gauss expressed the Gravitational constant in units of the Solar system rather than SI units 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°. In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. This is currently on or close to 1 January. It is named after the 19th century German astronomer and mathematician Friedrich Bessel. The 19th century of the Common Era began on January 1, 1801 and ended on December 31, 1900, according to the Gregorian calendar Friedrich Wilhelm Bessel (22 July 1784 &ndash 17 March 1846 was a German Mathematician, Astronomer, and systematizer of the Bessel functions An approximate formula to compute the current time in Besselian years from the Julian day is:

B = 2,000 + (JD - 2,451,544. The Julian date (JD is the interval of time in days and fractions of a day since 4713 B 53) /365. 242189

### Great year

The Great year, Platonic year, or Equinoctial cycle corresponds to a complete revolution of the equinoxes around the ecliptic. A Great year (also known as a Platonic year or Equinoctial cycle) is the time required for one complete cycle of the Precession of the equinoxes, 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. The galactic year, also known as a cosmic year, is the duration of time required for the Solar system to Orbit once around the center of the Milky The Solar System consists of the Sun and those celestial objects bound to it by Gravity. The Galactic Center is the rotational center of the Milky Way Galaxy. 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. In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from
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. A separate article treats the phenomenon of Tidal resonance in Oceanography. Tidal drag in turn depends on factors such as post-glacial rebound and sea level rise. Post-glacial rebound (sometimes called continental rebound, isostatic rebound, isostatic adjustment or post-ice-age isostatic recovery) Sea-level rise is an increase in Sea level. Multiple complex factors may influence this change
• 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. The solar wind is a Stream of charged particles&mdasha plasma &mdashthat are ejected from the upper atmosphere of the Sun. 25 microsecond per year[1]). To help compare Orders of magnitude of different Times this page lists times between 10&minus6 seconds and 10&minus5 seconds (1 micro
• Other effects tend to shorten the Earth's orbital period: the Poynting-Robertson effect (about 30 nanoseconds per year). The Poynting-Robertson effect, also known as Poynting-Robertson drag, named after John Henry Poynting and Howard Percy Robertson, is a process by which A nanosecond ( ns) is one billionth of a second See also times of other orders of magnitude. And the gravitational radiation (by about 165 attoseconds per year[2]) . In Physics, a gravitational wave is a Fluctuation in the Curvature of Spacetime which propagates as a wave, traveling outward from To compare various Orders of magnitude of Time units this page lists units of time between 10&minus18 and 10&minus15 seconds (i . .

## Summary of various kinds of year

• 346. 62 days - a draconitic year in some septenary calendars. 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
• 353, 354 or 355 days — the lengths of common years in some lunisolar calendars. A lunisolar calendar is a Calendar in many Cultures whose date indicates both the Moon phase and the time of the solar Year.
• 354. 37 days/12 lunar months - the average length of a year in lunar calendars. A lunar calendar is a Calendar that is based on cycles of the Moon phase.
• 365 days — a common year in many solar calendars. A common year is a common type of Calendar year. It has exactly 365 days and so is not a Leap year. A solar calendar is a Calendar whose dates indicate the position of the earth on its revolution around the Sun (or equivalently the apparent position of the sun moving
• 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. A leap year (or intercalary year) is a year containing one or more extra days (or in the case of Lunisolar calendars an extra month in order to keep the
• 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. A day (symbol d is a unit of Time equivalent to 24 Hours and the duration of a single Rotation of planet Earth with respect to the 1775 weeks, 8,765. A week (also called sennight or sevennight) is a unit of Time longer than a Day and shorter than a Month. 82 hours = 525,949. The hour (symbol h) is a unit of Time. It is not an SI unit but is accepted for use with the SI 2 minutes = 31,556,952 seconds (mean solar, not SI). A minute is a Unit of measurement of Time or of Angle. The minute is a unit of Time equal to 1/60th of an Hour or 60 The second ( SI symbol s) sometimes abbreviated sec, is the name of a unit of Time, and is the International System of Units
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. The Gregorian calendar is the most widely used Calendar in the world today

## 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. A calendar era is the year numbering system used by a Calendar. 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. Jesus of Nazareth (7–2 BC / BCE —26–36 AD / CE) 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

1. ^ Solar mass is ~2×1030 kg, decreasing at ~5×109 kg/s, or ~8×10−14 solar mass per year. The period of an orbiting body is proportional to $\frac{1}{\sqrt{M}}$, where M is the mass of the primary.
2. ^ ~300 W of radiation produces ~9. 5×109 J orbital energy decrease per year; this varies as 1/R, and period varies as R1. 5

In current use Assyrian calendar Astronomical year numbering Bahá'í calendar Bengali calendar Annum is one form of the Latin noun meaning Year, not a form normally used for derivatives in modern languages the accusative singular 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common

## year

### -noun

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).
2. (by extension) The time it takes for any planetary body to make one revolution around another body.
3. A period between set dates that mark a year, from January 1 to December 31 by the Gregorian calendar.
4. A scheduled part of a calendar year spent in a specific activity.
5. (sciences) A Julian year, exactly 365.25 days, represented by "a".
6. A level or grade in school or college.
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