This is a list of

calendar A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A date is the designation of a single and specific day within such a system. A calendar is also a physi ...

s. Included are historical calendars as well as proposed ones. Historical calendars are often grouped into larger categories by cultural sphere or historical period; thus O'Neil (1976) distinguishes the groupings

Egyptian calendar The ancient Egyptian calendar – a civil calendar – was a solar calendar with a 365-day year. The year consisted of three seasons of 120 days each, plus an intercalary month of five epagomenal days treated as outside of the year proper. Eac ...

s (Ancient Egypt), Babylonian calendars (Ancient Mesopotamia), Indian calendars (Hindu and Buddhist traditions of the Indian subcontinent),

Chinese calendar The traditional Chinese calendar (also known as the Agricultural Calendar ��曆; 农历; ''Nónglì''; 'farming calendar' Former Calendar ��曆; 旧历; ''Jiùlì'' Traditional Calendar ��曆; 老历; ''Lǎolì'', is a lunisolar calendar ...

s and Mesoamerican calendars. These are not specific calendars but series of historical calendars undergoing reforms or regional diversification. In Classical Antiquity, the

Hellenic calendars Various ancient Greek calendars began in most states of ancient Greece between Autumn and Winter except for the Attic calendar, which began in Summer. The Greeks, as early as the time of Homer, appear to have been familiar with the division of the ...

inspired the Roman calendar, including the solar Julian calendar introduced in 45 BC. Many modern calendar proposals, including the Gregorian calendar introduced in 1582 AD, contains modifications from that of the Julian calendar.

List of calendars

In the list below, specific calendars are given, listed by calendar type (solar, lunisolar or lunar), time of introduction (if known), and the context of use and cultural or historical grouping (if applicable). Where appropriate, the regional or historical group ( Jewish calendar, Hijri calendar, Mayan, Aztecan,

Egyptian Egyptian describes something of, from, or related to Egypt. Egyptian or Egyptians may refer to: Nations and ethnic groups * Egyptians, a national group in North Africa ** Egyptian culture, a complex and stable culture with thousands of years of ...

Mesopotamian Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the F ...

, Iranian,

Hindu Hindus (; ) are people who religiously adhere to Hinduism.Jeffery D. Long (2007), A Vision for Hinduism, IB Tauris, , pages 35–37 Historically, the term has also been used as a geographical, cultural, and later religious identifier for ...

, Buddhist, Pre-Columbian Mesoamerican, Hellenic,

Julian Julian may refer to: People * Julian (emperor) (331–363), Roman emperor from 361 to 363 * Julian (Rome), referring to the Roman gens Julia, with imperial dynasty offshoots * Saint Julian (disambiguation), several Christian saints * Julian (give ...

or Gregorian-derived) is noted. Calendars fall into four types: lunisolar,

solar Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...

lunar Lunar most commonly means "of or relating to the Moon". Lunar may also refer to: Arts and entertainment * ''Lunar'' (series), a series of video games * "Lunar" (song), by David Guetta * "Lunar", a song by Priestess from the 2009 album ''Prior t ...

and seasonal. Most pre-modern calendars are lunisolar. The seasonal calendars rely on changes in the environment (e.g., "wet season", "dry season") rather than lunar or solar observations. The Islamic and some Buddhist calendars are lunar, while most modern calendars are solar, based on either the Julian or the Gregorian calendars. Some calendars listed are identical to the Gregorian calendar except for substituting regional month names or using a different calendar epoch. For example, the Thai solar calendar (introduced 1888) is the Gregorian calendar using a different epoch (543 BC) and different names for the Gregorian months (Thai names based on the signs of the zodiac).

Variant month names

Regional or historical names for lunations or Julian/Gregorian months

Non-standard weeks

Calendaring and timekeeping standards

* Coordinated Universal Time, adopted 1960 and since 1972 including a system of observation-based leap seconds. * ISO 8601, standard based on the Gregorian calendar, Coordinated Universal Time and ISO week date, a leap week calendar system used with the Gregorian calendar * Fiscal year varies with different countries. Used in accounting only. *

360-day calendar The 360-day calendar is a method of measuring durations used in financial markets, in computer models, in ancient literature, and in prophetic literary genres. It is based on merging the three major calendar systems into one complex clock, with ...

used for accounting *

365-day calendar A 365-day calendar consists of exactly 365 days per year (in common years), and is primarily used in computer models and as an assumption in every-day calculations. For example, a calculation of a daily rate may use an annual total divided by exactl ...

used for accounting * Unix time, number of seconds elapsed since 1 January 1970, 00:00:00 (UTC). *

Julian day The Julian day is the continuous count of days since the beginning of the Julian period, and is used primarily by astronomers, and in software for easily calculating elapsed days between two events (e.g. food production date and sell by date). ...

, number of days elapsed since 1 January 4713 BC, 12:00:00 (UTC). *

Heliocentric Julian Date The Heliocentric Julian Date (HJD) is the Julian Date (JD) corrected for differences in the Earth's position with respect to the Sun. When timing events that occur beyond the Solar System, due to the finite speed of light, the time the event is obs ...

, Julian day corrected for differences in the Earth's position with respect to the Sun. *

Barycentric Julian Date The Barycentric Julian Date (BJD) is the Julian Date (JD) corrected for differences in the Earth's position with respect to the barycentre of the Solar System. Due to the finite speed of light, the time an astronomical event is observed depends on ...

, Julian day corrected for differences in the Earth's position with respect to the barycentre of the Solar System. *

Lilian date A Lilian date is the number of days since the beginning of the Gregorian calendar on October 15, 1582, regarded as Lilian date 1. It was invented by Bruce G. Ohms of IBM in 1986 and is named for Aloysius Lilius, who devised the Gregorian Calendar. ...

, number of days elapsed since the beginning of the Gregorian Calendar on 15 October 1582. * Rata Die, number of days elapsed since 1 January 1 AD 1 in the proleptic Gregorian calendar.

Non-Earth or fictional

Darian calendar The Darian calendar is a proposed system of timekeeping designed to serve the needs of any possible future human settlers on the planet Mars. It was created by aerospace engineer, political scientist, and space jurist Thomas Gangale in 1985 and ...

(proposed for Mars, not used in planetary science) *

Discworld calendar The Discworld is the fictional setting for all of Terry Pratchett's ''Discworld'' fantasy novels. It consists of a large disc (complete with edge-of-the-world drop-off and consequent waterfall) resting on the backs of four huge elephants which ar ...

(fictional) *

Middle-earth calendar In J. R. R. Tolkien's legendarium, the history of Arda, also called the history of Middle-earth, began when the Ainur entered Arda, following the creation events in the Ainulindalë and long ages of labour throughout Eä, the fictional univer ...

s (fictional) *

Stardate ''StarDate'' is a science radio program of The University of Texas at Austin McDonald Observatory, broadcast on over 360 radio stations. It is a daily guide to the night sky and breaking astronomical news. Typically heard without formal introdu ...

s (from

Star Trek ''Star Trek'' is an American science fiction media franchise created by Gene Roddenberry, which began with the eponymous 1960s television series and quickly became a worldwide pop-culture phenomenon. The franchise has expanded into vari ...

, fictional)

References