Year

The Year ( Old High German jar, Latin annus ) is a period of time, depending on the definition has a different length:

In the astronomical sense a year the period of a complete revolution of a celestial object around a star. In a narrower sense, the Earth year is meant as the duration of the earth orbit around the sun. Distinction is made between the sidereal year, tropical year and distinguished anomalistischem year, the last with small mutual deviations all about 365 ¼ days.
The most common is the calendar year, based on the tropical year, meant. Both in the Julian calendar and the Gregorian calendar, it takes either 365 days ( common year ) or 366 days ( leap year). In everyday life we mean by the term " year " means the respective time of New Year's Eve up.
From the Calendar account to any other annual divisions are culturally (eg school year, Memorial year) or individually marked (eg age ).
Phenological years include the cycle of the four seasons. They usually are based on certain natural events in sequence.

4.1 Personal Years
Memorial 4.2 years

Calendar year

The present world-wide standard and - particularly in Europe - legally valid calendar is the Gregorian calendar.

Thus, the standard makes a statement at the times of the beginning and end of the year, but not to the intervening elapsed time. In addition to the normal common year to 365 days, the Gregorian calendar has leap years to 366 days - as the Julian calendar, but used other switching rules.

For the calendar year, the term is widespread civic year ( the term bourgeois era 'refers to the distinction, physically ' or ' astronomical ').

Thus, the length of a year results (Gregorian ) to:

Where a calendar day ( 00:00-24:00 ) in length generally the SI day to 86,400 seconds equivalent, ie normally:

Occasionally the calendar yearly length is modified by the insertion of leap seconds. The seconds are on June 30th or 31st of December when necessary pasted March 31 or September 30, making this calendar days may be one second longer.

By switching days, the average calendar year will be adapted to the tropical year. The leap seconds, however, are used to adjust the average calendar day to the average solar day, through them, the world time UTC ( coordinated universal time ) with the universal time UT ( universal time ) and the Atomic Time TAI is so coordinated.

The year is divided into 12 months. These vary in the Gregorian calendar in length.

A calendar year lasts 52 weeks ( 7 days ) and one or two days. A calendar week is from Monday to Sunday and is counted regardless of the year, so that 52 or 53 calendar weeks may fall in one year. First Week of the year is the week " fall into at least four of the first 7 days of January ", ie, January 4th is always in the first calendar week.

The long-term mean length of the calendar year according to the Gregorian calendar (ignoring leap seconds ):

The length is calculated from the fact that after the firing rules of the Gregorian calendar within 400 years of each 97 leap days are added. These rules try, as with all solar calendars, the calendar year of the true orbital period of the Earth around the Sun - the tropical year - as simple as possible, yet sufficiently accurate to approximate (see → Astronomy section).

From the perspective of physical metrology provides a " year " (without specifying the base) no unit of measure is, in the International System of Units, a unit symbol a is tolerated in certain contexts. A mandatory standard for the length of a year, there is not, the above values are as before but more specific normative foundations.

Date

Water Snake (癸巳, 30) - Wood Horse (甲午, 31)

The calendar years, starting consecutively numbered according to the ISO 8601 from the year zero with the year. In order for a single calendar year is clearly described, and is the basic size of the era and part of the calendar date. Depending on the date format it will be listed two or four digits.

Economic and statistical definitions

There are also numerous other marketing years:

The hunting season begins on 1 April and ends on 31 March of the following calendar year. The hunting season is used for creating routes statistics and usually the duration of hunting lease times in the hunting leases is stated on the hunting season.

Definitions in other calendars

Other calendar systems than the Gregorian calendar used both different definition of length and the beginning of a year, as well as other reference data so other year figures. In mid-2006, for example, according to the Islamic calendar, the year 1427 in the Jewish Calendar 5766, in the traditional Chinese calendar丙戌" Fire Dog ".

Other basic parameters of the length of the year are:

Other special calendar years see the list of calendar systems.

As Kinky year is defined as the longest calendar year in history, the (46 BC) occurred during the introduction of the Julian calendar, it was 445 days long; see also the year zero. The shortest year was 1582, when 10 days were skipped by the introduction of the Gregorian calendar. The longest year in the Gregorian calendar was 1972 a leap year one day and two leap seconds longer than usual. More than a leap second in a single year since then was never more necessary and therefore seems not to be foreseen to be provided.

Years definitions of Geosciences

To describe the time between two natural events as the year, corresponding to the original and intuitive concept of annual flow as the cycle of the seasons. This can be, for instance the period between two spring flooding of a stream to certain bird migrations, agricultural events, or the first frost. Definitions in this sense are:

For geological dating of the zero point of the calendar is irrelevant, here are generally one year in, year millions before today ' to: million years ago ( mya ), besides also bya is for billion years ago, billions of years before present ' possible. Periods are then given in Ma (Mega years ), in English-speaking countries with yr instead of a

Astronomical definitions

Without further additives with " year" means the solar year meant:

" Circulation" is a question of the reference points, but move constantly due to the complex forces and motion conditions in the solar system, so there are some very specific definitions. The exact lengths are subject to short-and medium-term periodic fluctuations, therefore, mean values are given below. These are also subject to long-term ( " secular " ) changes, so must be specified for high accuracy, a reference date. Below this is the standard epoch J2000.0.

The Bessel solar year was the basic size of the outdated Bessel era. It corresponds to the length of the tropical year.

In principle, it is generally the time between two repetitions of an event related to the orbit of any astronomical object around its central object, ie each complete circulation, referred to as a year. A revolution of the Earth around the Sun is an Earth year in this sense.

A sidereal Mercury year lasts, for example, almost 88 days, one Mars year approximately 687 days and that of Pluto 90,465 days, so 248 years - so far, the term 'year' including the orbital period is synonymous, but for obvious reasons for moons ( here called they month), satellite, etc. not used.
The heliacal year is the interval between two successive heliacal wells of a fixed star. The length and the beginning of such year is dependent on the geographic width and position of the star.
The eclipse year ( erroneously also: the drakonitische year) the time interval between two passages of the sun through the same lunar node. It is related to solar and lunar eclipses. The length is approximately 346.62 days = 346 d 15 h
Platonic year is a name for the cycle of precession: It is the time of a complete revolution of the Earth's axis on the cone, which is described by the precession and takes about 25700-25800 Jahre
The Galactic year is the full orbit of the Sun - and our planetary system - around the galactic center. It takes about 220-240 million years.

Irrespective of this, in astronomy, the term " year " used as a measure of time. In this case, so that is a period of 365.25 days meant to 86,400 SI seconds, the average length of a year in the Julian calendar. The reason for this is that this unit matches the one hand, quite accurately with the length of the solar year and one the other hand, simply can count on. For long-term calculations, the units Julian century ( 36,525 days ) and Julian millennium be used. This does not mean that astronomers would use the Julian calendar. For dates use the usual bourgeois (ie Gregorian) calendar or the Julian date.

Definitions in a different cultural context

Personal years

In distinction to the other definitions, some are given over the years to individual chronological key data, so specific, personal events. These are based not on the cyclical chronology of the calendar, but on the linear chronology of human life.

Memorial years

Years serving the memory of a people or the memory of an event. These include the references of many a calendar year accounting systems ( dynastic calendar) after the accession of a ruler, in a broader sense, the year one of the most calendar systems.

Julian year

The Julian year is a unit of measurement derived from the one-year term of time and corresponds to a time of exactly 365.25 days. It corresponds to the average of the lengths of the year in the Julian calendar, and is in contrast to the Julian calendar year an exact, consistent unit of measurement. Use it finds in the field of astronomy, when there is generally spoken of a " year ".

Larger units

Years are brought together to a decade (decade ), Century ( Hektode ), Millennium (Millennium ). Year Ten Thousand ( Deka Millennium ), hundreds of thousands of years ( Hektamillennium ). For extremely long periods of time you actually use the prefixes for units:

Ma ( in the English language also Myr ) is an abbreviation for a million years ( mega- annum).
Ga ( in the English language also Gyr ) is an abbreviation for a billion years ( Giga - year).

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