Do You Know What a Year Is? - DATAVERSITY (2023)

byMichael Brackett

As the calendar year comes to a close, a new one begins, and the fear of a December 21, 2012, catastrophe fades away, the meaning of a year comes to mind. Data resource managers deal with a wide variety of different years, and those different years need to be formally named and comprehensively defined to be meaningful and avoid any confusion.

Many people say “Well, everybody knows what a year is!”, and don’t see the need to precisely define a year. However, the problem is that the termYearmeans many different things to many different people, and is often used without being formally named or comprehensively defined. The result is misunderstanding, misuse of the data, and the creation of disparate data.

To comprehensively define the year being used in data resource design, the different types of years must be recognized and understood. Years can either be astronomical years or calendar years. The most prominent astronomical years are the sidereal year, anomalistic year, and equinoctial year.

Thesidereal yearis the time for the Earth to complete one revolution through its orbit, as measured against a fixed frame of reference. That reference is usually a star (Latin namestars) resulting in the namesidereal year. The duration of a sidereal year is 365.256363004 solar days (365 days, 6 hours, 9 minutes, and 9.76 seconds).

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Thenanomalistic yearis the time for the Earth to complete one revolution through its elliptical orbit (ecliptic), with respect to the extreme points (apsides) of that elliptical orbit. The apsides are the perihelion, where the Earth is closest to the Sun, and the aphelion where the Earth is farthest from the Sun. The anomalistic year is usually the time between perihelion passages. The duration of the anomalistic year is 365.259363 days (365 days, 6 hours, 13 minutes, and 53 seconds).

Thenequinoctial year, also known as thesolar tropical year, is the time for the ecliptic longitude of the sun to increase by 360 degrees, and is usually taken between vernal (spring) equinoxes. Since the Sun’s ecliptic longitude is measured with respect to the equinox, the equinoctial year comprises a complete cycle of the seasons. At 365.24219 days (365 days, 5 hours, 48 minutes, 45 seconds) it’s about 20 minutes shorter than the sidereal year.

Other less prominent, though often very useful, astronomical years are the draconic year, Sothic year, heliacal year, lunar year, Gaussian year, Besselian year, vague year, galactic year, and great year.

Thedraconic year, also known as thedraconitic yearand theeclipse year, is the length of time for the Sun, as seen from the Earth, to complete one revolution with respect to the same point where the Moon’s orbit intersects the Earth’s ecliptic (lunar node) and is associated with eclipses. Eclipses occur when both the Sun and the Moon are near these lunar nodes. Eclipses occur every half eclipse year giving two eclipse seasons in each eclipse year. A draconic year is 346.620075883 days (346 days, 14 hours, 53 minutes, 54 seconds).

TheSothic yearis the interval between heliacal risings of the star Sirius (ancient name Sothis). It originated in ancient Egypt when astronomers noticed that the start of the annual Nile floods coincided with the first visibility of Sothis. The Sothic year is shorter than the sidereal year and is very close to the Julian year.

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Theheliacal yearis the interval between the heliacal risings of any specific star. It differs from the sidereal year for stars away from the ecliptic due to the precession of the equinoxes.

Thelunar yearis twelve full cycles of the Moon phases, as seen from the Earth. It is approximately 354.37 days.

TheGaussian yearis the sidereal year for a planet of negligible mass compared to the Sun, that is unperturbed by other planets, and is governed by the Gaussian gravitational constant. Such a planet would be slightly closer to the Sun than the Earth. The Gaussian year would be 365.2568983 days (365 days, 6 hours, 9 minutes, and 56 seconds).

TheBesselian yearis a tropical year that starts when the Sun reaches an ecliptic mean longitude of 280 degrees. It’s named after the 19thcentury German astronomer and mathematician Friedrich Bessel. The Besselian year depends on the theory about the Earth’s orbit around the sun that was proposed by Newcomb in 1985, which is now obsolete. Hence the Besselian year is no longer used.

Thevague year, also known as awandering year, is an approximation to a year equaling 365 days, but wanders in relation to an exact year. A vague year consists of 12 schematic months of 30 days each plus 5 epagomenal days, totaling 365 days.

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Thegalactic yearis the time for the Earth’s Solar System to revolve once around the Milky Way galactic center. The duration of that revolution is approximately 230 million Earth years.

Thegreat year, also known as theequinoctial cycleorprecession of the equinoxes, is one complete revolution of the equinoxes around the ecliptic. Precession is the movement of the rotational axis of the Earth, where the axis slowly marks a cone around the ecliptic pole with an angular radius of 23.5 degrees, and moves one degree every 72 years. During precession the stars move slowly through equatorial coordinates and ecliptic longitudes. The length of a great year is slightly less than 26,000 years. However, it cannot be determined exactly because the precession speed is not constant.

Thecalendar yearis an approximation of the Earth’s orbital period stated as a calendar. Calendar years are typically Gregorian or Julian consisting of common years containing 365 days and leap years containing 366 days. However, other calendars, such as Chinese, Persian, Islamic, Hindu, and so on, also exist.

The equinoctial year is the basis for the Gregorian calendar. The Gregorian calendar can be used to form a variety of different years, such as a seasonal year, calendar year, fiscal year, academic year, and Julian year.

Aseasonal yearis the time between recurrences of a seasonal event, such as a river flooding, seasonal bird migration, flowering of plants, first frost, a sports event, and so on. A seasonal year can vary as much as a month or more from one calendar year to another year.

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Afiscal yearis a financial twelve-month period useful for preparing financial statements. Many jurisdictions have regulations requiring financial statements every twelve months, although those twelve months do not need to correspond to a calendar year. For example, in the United Statesstate fiscal yearsare July 1 through June 30, andfederal fiscal yearsare October 1 through September 30. Other countries have different fiscal years, such as the United Kingdom’s fiscal year runs from April 1 to March 31 for corporation tax and government financial statements, and April 6 to April 5 for personal taxation and payment of state benefits. Acorporate fiscal yearis exactly 52 weeks divided into four 13-week quarters. Organizations using the corporate fiscal year usually file for a change in the dates of their fiscal year every calendar year.

Anacademic yearis the annual period that a student attends an educational institution, and is usually divided into academic terms consisting of either four quarters or three semesters. Academic year dates vary widely among educational institutions, generally starting and ending sometime during the early Fall.

AJulian yearis defined as exactly 365.25 days, and is used in astronomy and other scientific contexts. AJulian centuryis 36525 days and aJulian millenniumis 365250 days. Expressing time in Julian years precisely specifies the number of days, not the number of years, and is used for long time intervals. Julian year is used in the computation of distances based on a light year.

For a large number of Julian years, the notations kiloannum (Ka) is 103(thousand) years, megaannum (Ma) is 106(million) years, gigaannum (Ga) is 109(billion) years, teraannum (Ta) is 1012(trillion) years, petaannum (Pa) 1015(quadrillion), and exaannum (Ea) 1018(quintillion) years are used. Kiloannum is used for geology, archeology, and paleontology. Megaannum is used for geology, paleontology, and celestial mechanics. Gigaaannum is used for geology and cosmology where the age of the Earth is 4.57 Ga. Tetraannum is 70 times longer than the age of the universe. Petaannum is the half-life of cadmium 113 at 8 Pa. Exaannum is the half-life of tungsten 180 at 1.8 Ea.

The years described above are with respect to the Earth and its Solar System. Other planets in the Solar System, and planets in other solar systems, will have different values for these years, or may have different years altogether.

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Professional data managers, particularly data architects and data modelers, must provide a formal name and comprehensive definition of the specific year being used in the data resource, and must specify the location, such as the Earth, the Solar System, the Milky Way Galaxy, or the universe.



Do You Know What a Year Is? - DATAVERSITY? ›

The duration of a sidereal year

A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky of a celestial body of the Solar System such as the Earth, completing a full cycle of seasons; for example, the time from vernal equinox to vernal equinox, or from summer solstice to summer ... › wiki › Tropical_year
is 365.256363004 solar days (365 days, 6 hours, 9 minutes, and 9.76 seconds). Then anomalistic year is the time for the Earth to complete one revolution through its elliptical orbit (ecliptic), with respect to the extreme points (apsides) of that elliptical orbit.

Why is a draconic year shorter than a year? ›

A draconic month is shorter than a sidereal month because the nodes precess in the opposite direction to that in which the Moon is orbiting Earth, one rotation every 18.6 years.

What are the types of years? ›

Astronomical years
  • Julian year.
  • Sidereal, tropical, and anomalistic years.
  • Draconic year.
  • Full moon cycle.
  • Lunar year.
  • Vague year.
  • Heliacal year.
  • Sothic year.

What is a year measured by? ›

A year is the time it takes for the earth to revolve around the sun once. A calendar year is 365 days. A solar or tropical year is 365 days, 5 hours, 48 minutes, and 46 seconds.

What do you know about year? ›

A year is about 365 days (except in a leap year). It is the time it takes the Earth to go completely around (orbit) the sun once. A year is actually almost 365.25 days long, but a calendar has 365 days, except in a leap year, which has 366 days.

What year is it scientifically? ›

The current year by the Gregorian calendar, AD 2023, is 12023 HE in the Holocene calendar. The HE scheme was first proposed by Cesare Emiliani in 1993 (11993 HE), though similar proposals to start a new calendar at the same date had been put forward decades earlier.

How long is a draconic year in days? ›

A draconic year is 346.620075883 days (346 days, 14 hours, 53 minutes, 54 seconds). The Sothic year is the interval between heliacal risings of the star Sirius (ancient name Sothis).

What was the 1st year called? ›

AD 1 or 1 CE is the epoch year for the Anno Domini (AD) Christian calendar era, and the 1st year of the 1st century and 1st millennium of the Christian and Common Era (CE).

Is there a year 001? ›

There is no year 0. Jesus was born before 4 B.C.E. The concept of a year "zero" is a modern myth (but a very popular one). In our calendar, C.E. 1 follows immediately after 1 B.C.E. with no intervening year zero.

What calendar did Jesus use? ›

The Julian calendar is the one that was introduced in the year 46 BC by Julius Caesar to all of the Roman Empire, and it is the calendar that was used during the life of Jesus Christ and at the time of the early Church.

What is the real year of the Earth? ›

Earth is estimated to be 4.54 billion years old, plus or minus about 50 million years. Scientists have scoured the Earth searching for the oldest rocks to radiometrically date.

How long was a year originally? ›

Before then, the Romans knew that it took about 365.25 days for the Earth to orbit the sun, but they decided to stick to a 355 day calendar anyway. Every so often the high priest of Rome would call for an “intercalary month” to put the calendar back on track.

How long is a celestial year? ›

An astronomical year is defined to be exactly 365.25 days (31,557,600 seconds), where days are exactly 24 hours (86,400 seconds) long.

What is a year based on? ›

Our concept of a year is based on the earth's motion around the sun. The time from one fixed point, such as a solstice or equinox, to the next is called a tropical year. Its length is currently 365.242190 days, but it varies. Around 1900 its length was 365.242196 days, and around 2100 it will be 365.242184 days.

What are the two types of year? ›

These two years are the Fiscal year and Calendar year. The similarity between these years is that these last for 365 days or twelve consecutive months.

What makes the year? ›

A year is the amount of time it takes a planet to orbit its star one time. A day is the amount of time it takes a planet to finish one rotation on its axis. It takes Earth approximately 365 days and 6 hours to orbit the Sun. It takes Earth approximately 24 hours — 1 day — to rotate on its axis.

Why are years based on Jesus? ›

The Christian calendar was created by an Eastern European monk named Dionysius Exiguus. He invented the now commonly used Anno Domini (A.D.) era, which counts years based on the birth of Jesus. He came up with this concept in the year 525, or, 525 years after the birth of Jesus.

How accurate is our year? ›

According to scholars throughout history, we actually aren't living in the year that is printed on our calendars. The more the origins and development of dating systems have been and are studied, the more it becomes apparent that time is only what we make it.

What is the most accurate year? ›

The Solar Hijri Calendar

It is based on astronomical observations of the Sun and is the most accurate calendar in the world. Like the Islamic Hijri calendar, the year count for the Solar Hijri calendar also began with the Prophet Mohammed's migration to Medina in 622 CE.

How long is the sidereal year? ›

definition and length

…year is shorter than the sidereal year (365 days 6 hours 9 minutes 10 seconds), which is the time taken by the Sun to return to the same place in its annual apparent journey against the background of the stars.

What is 29.530589 days? ›

The mean time for one lunar phase cycle (i.e., the synodic period of the Moon) is 29.530589 days, or 29 days, 12 hours, 44 minutes, 3 seconds. More specifically, a lunation is also commonly defined as the mean time between successive new moons.

How many years is a Saros? ›

Fred Espenak. The periodicity and recurrence of eclipses is governed by the Saros cycle, a period of approximately 6,585.3 days (18 years 11 days 8 hours). It was known to the Chaldeans as a period when lunar eclipses seem to repeat themselves, but the cycle is applicable to solar eclipses as well.

What year did the world start? ›

When the solar system settled into its current layout about 4.5 billion years ago, Earth formed when gravity pulled swirling gas and dust in to become the third planet from the Sun.

What was the first year on Earth like? ›

In Earth's Beginning

At first, it was extremely hot, to the point that the planet likely consisted almost entirely of molten magma. Over the course of a few hundred million years, the planet began to cool and oceans of liquid water formed.

What was the first year on Earth recorded? ›

You can't get any earlier than that. The tradition of recording significant events in the history books started with the Sumerians in Mesopotamia around 2900 bc (OR POSSIBLY, sightly earlier in Egypt but this is a more controversial theory).

What year was Jesus born? ›

The date of birth of Jesus is not stated in the gospels or in any historical sources, but most biblical scholars generally accept a date of birth between 6 BC and 4 BC, the year in which King Herod died.

How long ago was Jesus born? ›

Jesus was born around 4 B.C. and was crucified in A.D. 30, according to the PBS FRONTLINE show "From Jesus to Christ." Britannica cites his birth year as ranging from 6 to 4 B.C.

Did the year 999 exist? ›

Year 999 (CMXCIX) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar. Centuries: 9th century. 10th century.

Did Jesus live in BC or AD? ›

Using these methods, most scholars assume a date of birth between 6 and 4 BC, and that Jesus' preaching began around AD 27–29 and lasted one to three years. They calculate the death of Jesus as having taken place between AD 30 and 36.

Did there used to be 13 months? ›

The thirteenth month, placed between February and March, would be called Vern, due to its proximity to the vernal equinox and the beginning of spring. (Later versions of the bill dropped the name Vern and replaced it with the month of “Liberty.”)

What is the AD stand for? ›

AD stands for Anno Domini, Latin for “in the year of the Lord”, while BC stands for “before Christ”.

Who was the first person on Earth? ›

Adam is the name given in Genesis 1-5 to the first human. Beyond its use as the name of the first man, adam is also used in the Bible as a pronoun, individually as "a human" and in a collective sense as "mankind".

How old is the Earth according to Bible? ›

Concerning the age of the Earth, the Bible's genealogical records combined with the Genesis 1 account of creation are used to estimate an age for the Earth and universe of about 6000 years, with a bit of uncertainty on the completeness of the genealogical records, allowing for a few thousand years more.

How old is mankind on Earth? ›

Fossils and DNA suggest people looking like us, anatomically modern Homo sapiens, evolved around 300,000 years ago. Surprisingly, archaeology – tools, artefacts, cave art – suggest that complex technology and cultures, “behavioural modernity”, evolved more recently: 50,000-65,000 years ago.

When did humans start counting years? ›

A monk called Dionysius Exiguus (early sixth century A.D.) invented the dating system most widely used in the Western world. For Dionysius, the birth of Christ represented Year One. He believed that this occurred 753 years after the foundation of Rome.

When did the 7 day week originate? ›

For centuries the Romans used a period of eight days in civil practice, but in 321 CE Emperor Constantine established the seven-day week in the Roman calendar and designated Sunday as the first day of the week.

How did ancients know how long a year was? ›

Celestial bodies — the Sun, Moon, planets, and stars — have provided us a reference for measuring the passage of time throughout our existence. Ancient civilizations relied upon the apparent motion of these bodies through the sky to determine seasons, months, and years.

Is there a galactic year? ›

The galactic year, also known as a cosmic year, is the duration of time required for the Sun to orbit once around the center of the Milky Way Galaxy. One galactic year is 230 million Earth years.

How many years is a star? ›

The exact lifetime of a star depends very much on its size. Very massive stars use up their fuel quickly. This means they may only last a few hundred thousand years. Smaller stars use up fuel more slowly so will shine for several billion years.

How many galactic years are there? ›

Our place in the galaxy

What we Earthlings call a galactic year is specific to Earth's place in the Milky Way's spiral. "We would say that a galactic year is 220, 230 million years. Other stars in the galaxy, their galactic year is different," Hawkins said.

What is the original calendar? ›

A mesolithic arrangement of twelve pits and an arc found in Warren Field, Aberdeenshire, Scotland, dated to roughly 8,000 BC, has been described as a lunar calendar and was dubbed the "world's oldest known calendar" in 2013.

What is a year known as? ›

The calendar year is also called the civil year and contains a full 365 days or 366 for a leap year. It is divided up into months, weeks, and days. The Gregorian calendar is the international standard and is used in most parts of the world to organize religious, social, business, personal, and administrative events.

What year is it in all the calendars? ›

Current year according to various historical and world calendars, as of January 1. 2023
CharacteristicCurrent year
6 more rows
Jan 2, 2023

What are the 4 periods of year? ›

A season is a period of the year that is distinguished by special climate conditions. The four seasons—spring, summer, fall, and winter—follow one another regularly. Each has its own light, temperature, and weather patterns that repeat yearly.

What year is the Mayan calendar? ›

The Maya Calendar. The Maya calendar in its final form probably dates from about the 1st century B.C., and may originate with the Olmec civilization.

How do years work? ›

Under the Gregorian Calendar the year is divided into 365 (or 366 in a leap year) days which are then grouped into twelve months. The years are numbered according to the year in which Christ was believed to have been born.

Did the years start at year 1? ›

This calendar era is based on the traditionally reckoned year of the conception or birth of Jesus, AD counting years from the start of this epoch and BC denoting years before the start of the era. There is no year zero in this scheme; thus the year AD 1 immediately follows the year 1 BC.

What was the first year number? ›

The "basic" format for year 0 is the four-digit form 0000, which equals the historical year 1 BC.

Is a sidereal year shorter than a tropical year? ›

The sidereal year is 20 min 24.5 s longer than the mean tropical year at J2000. 0 (365.242 190 402 ephemeris days). At present, the rate of axial precession corresponds to a period of 25,772 years, so sidereal year is longer than tropical year by 1,224.5 seconds (20 min 24.5 s, ~365.24219*86400/25772).

How long is draconic month? ›

The draconic, or nodical, month of 27.212220 days (i.e., 27 days 5 hours 5 minutes 35.8 seconds) is the time between the Moon's passages through the same node, or intersection of its orbit with the ecliptic, the apparent pathway of the Sun.

Is the sidereal year shorter than the eclipse year? ›

An eclipse year is shorter than a sidereal year because the nodes of the Moon's orbit regress westwards around the ecliptic by about 19° per year.

Is an eclipse year shorter or longer than a sidereal year? ›

Likewise, as seen from the Earth, the Sun passes both nodes as it moves along its ecliptic path. The period for the Sun to return to a node is called the eclipse or draconic year: about 346.6201 days, which is about 1⁄20 year shorter than a sidereal year because of the precession of the nodes.

How long is a sideral year? ›

A sidereal year is 365 days, 6 hours, 9 minutes, and 10 seconds. A solar year is the time it takes for the Sun to come from and return to the vernal equinox. A solar year is slightly shorter than a sidereal year due to Earth's slight wobble on its axis. One solar year is 365 days, 5 hours, 48 minutes, and 46 seconds.

How long is a true year? ›

A year is 365.24 days long — that's why we have to skip a leap day every 100 years.

What races speak draconic? ›

Draconic language is one of the most unique Dungeons and Dragons languages. Spoken mainly by the Dragons, it's a rare and secret language. The other speakers include only draconic-related natives, such as kobolds and Dragonborn, or reptilian races: Troglodytes and Lizardfolk.

What language would draconic be? ›

Scholars from Candlekeep theorized Draconic was created by the ignidracos, one of the ancestor species of true dragons. Draconic was a monolithic language, and it remained almost unchanged since its creation. The only known Draconic language variant was Aragrakh, an ancient draconic language.

What is draconic period? ›

draconic month (plural draconic months) A period of time between two consecutive passages of the Moon through the same orbital node. The draconic month is shorter than the sidereal month, due to precession of the Moon's orbit. An average one lasts 27 days, 5 hours, 5 minutes, 35.8 seconds.

Why are there 366 sidereal days? ›

Consequently, in 365 days, the Earth turns 366 times upon its axis; and as every rotation of the Earth upon its axis completes a “sidereal day,” there must be 366 sidereal days in a year.

How old is sidereal astrology? ›

These differences have caused sidereal and tropical zodiac systems, which were aligned around 2,000 years ago when the March equinox coincided with Aries in the observable sky, to drift apart over the centuries.

Who discovered sidereal year? ›

Aryabhata determined the sidereal day to be 23 hours, 56 minutes, and 4.1 seconds. Compare the value you obtained to that of the great Indian astronomer.

Is sidereal year longer? ›

The sidereal period of the Earth is 365.25636 mean solar days, which is slightly longer than the tropical year (measured between successive vernal equinoxes) of 365.24219. In most calendar systems, the length of the year is taken to be 365 days, which is close to the Earth's sidereal period.

Would we have 365 days in a year if we follow sidereal days? ›

A sidereal year is then the time taken by the Earth to travel in its orbit around the Sun and return to this exact position. The sidereal year has a length of 365 days, 6 hours, 8 minutes, 38 seconds (365.256 days). This is NOT, however, the year we actually use for calendrical purposes.

Why is a sidereal day 4 minutes shorter than a solar day? ›

The difference between the sidereal and solar day is due to the orbital motion of the planet. For the planets with their orbital motion in the same direction as their rotation (Mercury, Earth, Mars, Jupiter, Saturn, and Neptune), the solar day is longer than the sidereal day.


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