# List of calendars

This is a list of calendars. 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 calendars (Ancient Egypt), Babylonian calendars (Ancient Mesopotamia), Indian calendars (Hindu and Buddhist traditions of the Indian subcontinent), Chinese calendars and Mesoamerican calendars. These are not specific calendars but series of historical calendars undergoing reforms or regional diversification.
In Classical Antiquity, the Hellenic calendars 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, Sikh, Mayan, Aztecan, Egyptian, Mesopotamian, Iranian, Hindu, Buddhist, Pre-Columbian Mesoamerican, Hellenic, Julian or Gregorian-derived) is noted.
Calendars fall into four types: lunisolar, solar, lunar 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).
| Name | Type | Group | Introduction | Usage | Comments |
| Hebrew/Jewish Calendar | lunisolar | Canaan/Mesopotamian | Circa 3761 BC | Western World | It is based on lunar months with the intercalation of an additional month every 2 to 3 years to bring the cycle closer to the solar cycle. It is used to determine the dates for Jewish holidays and the appropriate public reading of Torah portions, yahrzeits (dates that commemorate the death of a relative), daily Psalm readings, and many other holidays, festivals and ceremonial uses. |
| Egyptian calendar | fixed (365 days) | Egyptian | Bronze Age | Middle Kingdom | The year is based on the heliacal rising of Sirius (Sothis) and divided into the three seasons of akhet (Inundation), peret (Growth) and shemu (Harvest). The heliacal rising of Sothis returned to the same point in the calendar every 1,460 years (a period called the Sothic cycle). |
| Umma calendar | lunisolar | Mesopotamian | Bronze Age | Sumer/Mesopotamia | Recorded in Neo-Sumerian records (21st century BC), presumably based on older (Ur III) sources. |
| Pentecontad calendar | solar | Mesopotamian | Bronze Age | Amorites | A Bronze Age calendar in which the year is divided into seven periods of fifty days, with an annual supplement of fifteen or sixteen days for synchronisation with the solar year. |
| Four Seasons and Eight Nodes | solar | Chinese | Bronze Age(?) | China | The years is divided into four seasons, and each season is divided into a festival and three months. The start and middle of each season is the key node of the year. |
| Gezer Calendar | unknown | Mesopotamian | 1000 BC | Israel/Canaan | The years are divided into monthly or bi-monthly periods and attributes to each a duty such as harvest, planting, or tending specific crops. |
| Roman calendar | lunisolar | Roman | 713 BC | Roman Republic | Based on the reforms introduced by Numa Pompilius in c. 713 BC. |
| Six Ancient Calendars | lunisolar | Chinese | Iron Age | China | Six classical (Zhou era) calendars: Huangdi, Zhuanxu, Xia, Yin, Zhou's calendar and Lu. |
| Nisg̱a'a | seasonal / lunisolar | Indigenous North America | | Nisg̱a'a | The Nisga’a calendar revolves around harvesting of foods and goods used. The original year followed the various moons throughout the year. |
| Inuit | seasonal | Indigenous North America | | Inuit | The Inuit calendar is based on between six and eight seasons as solar and lunar timekeeping methods do not work in the polar regions. |
| Haab' | fixed (365 days) | Pre-Columbian (Maya) | 1st millennium BC | Maya | |
| Tzolk'in | fixed (260 days) | Pre-Columbian (Maya) | 1st millennium BC | Maya | |
| Xiuhpohualli | fixed (365 days) | Pre-Columbian (Aztec) | | Aztecs | |
| Tonalpohualli | fixed (260 days) | Pre-Columbian (Aztec) | | Aztecs | |
| Attic calendar | lunisolar (354/384 days) | Hellenic | 6th century BC | Classical Athens | The year begins with the new moon after the summer solstice. It was introduced by the astronomer Meton in 432 BC. Reconstructed by Academy of Episteme. |
| Old Persian calendar | lunisolar(?) | Iranian | 4th century BC(?) | Persian Empire | Based on earlier Babylonian/Mesopotamian models |
| Seleucid calendar | lunisolar | Hellenic/Babylonian | 4th century BC | Seleucid Empire | Combination of the Babylonian calendar, ancient Macedonian (Hellenic) month names and the Seleucid era. |
| Genesis Calendar | lunisolar | Chinese | Han dynasty | China | Introduced the "month without mid-climate is intercalary" rule; based on a solar year of 365385⁄1539 days and a lunar month of 2943⁄81 days (19 years=235 months=693961⁄81 days). |
| Ptolemaic calendar | solar | Egyptian | 238 BC | Ptolemaic Egypt | The Canopic reform of 238 BC introduced the leap year every fourth year later adopted in the Julian calendar. The reform eventually went into effect with the introduction of the "Alexandrian calendar" (or Julian calendar) by Augustus in 26/25 BC, which included a 6th epagomenal day for the first time in 22 BC. |
| Julian calendar | solar | Roman | 45 BC | Western World | Revision of the Roman Republican calendar, in use in the Roman Empire and the Christian Middle Ages, and remains in use as liturgical calendar of Eastern Orthodox Churches. |
| Kurdish calendar | solar | Kurdish | Kurdistan | Kurdistan Region | is a calendar used in the Kurdistan region of Iraq alongside the Islamic and Gregorian calendar. The First day in this month is called "Newroz" it means "New Day". The start of the calendar is marked by the Battle of Nineveh, a conquest of the Assyrians by the Medes and the Babylonians in 612 BC. |
| Coptic calendar | solar | Egyptian | 1st century | Coptic Orthodox Church | Based on both the Ptolemaic calendar and the Julian calendar |
| Ge'ez calendar | solar | Ethiopian | 1st century | Ethiopia, Ethiopian Christians, Eritrea, Eritrean Christians | the calendar associated with Ethiopian and Eritrean Churchs, based on the Coptic calendar |
| Berber calendar | solar | Julian | In Roman times | North Africa | Julian calendar used for agricultural work. |
| Qumran calendrical texts | fixed (364 days) | — | c. 1st century | Second Temple Judaism | Description of a division of the year into 364 days, also mentioned in the pseudepigraphical Book of Enoch (the "Enoch calendar"). |
| Coligny calendar | lunisolar | Gauls/Celts | Iron Age | Gauls/Celts | Early calendar used by Celtic peoples prior to the introduction of the Julian calendar, on a bronze plaque c. AD 200 but likely some centuries older. |
| Zoroastrian calendar | fixed (365 days) | Iranian | 3rd century | Sassanid Persia | Based on both the Old Persian and Seleucid (Hellenic) calendars. Introduced in AD 226, reformed in AD 272, and again several times in the 5th to 7th centuries. |
| Chinese Calendar, Dàmíng origin | lunisolar | Chinese | 510 | China | Created by Zu Chongzhi, most accurate calendar in the world at its invention |
| Korean calendar | lunisolar | Chinese-derived | 6th century | Korea | Introduced from China, went through Korea to Japan. |
| Japanese calendar | lunisolar | Chinese-derived | 6th century | Japan | Umbrella term for calendars historically and currently used in Japan, in the 6th century derived from the Chinese calendar. |
| Chinese Calendar, Wùyín origin | lunisolar | Chinese | 619 | China | First Chinese calendar to use the true moon motion |
| Islamic calendar (Lunar Hijri calendar) | lunar | Muslim | 632 | Islam | Based on the observational lunisolar calendars used in Pre-Islamic Arabia. Remains in use for religious purposes in most of the Islamic world. |
| Pyu calendar | lunisolar | Hindu/Buddhist-derived | 640 | mainland Southeast Asia | Traditional calendar of Southeast Asia, in use until the 19th century. Traditionally said to originate in 640 (the calendar era) in Sri Ksetra Kingdom, one of the Burmese Pyu city-states. |
| Byzantine calendar | solar | Julian | 988 | Ecumenical Patriarchate of Constantinople | Julian calendar with Anno Mundi era in use c. 691 to 1728. |
| Armenian calendar | fixed (365 days) | Iranian | medieval | medieval Armenia | Calendar used in medieval Armenia and as liturgical calendar of the Armenian Apostolic Church. Derived from the Zoroastrian (or related medieval Iranian calendars such as the Sogdian/Choresmian ones). It uses the era AD 552. In modern Armenian nationalism, an alternative era of 2492 BC is sometimes used. |
| Bulgar calendar | solar | Bulgarian | Bronze Age | Volga Bulgaria | A reconstruction based on a short 15th-century transcript in Church Slavonic called Nominalia of the Bulgarian Khans, which contains 10 pairs of calendar terms. |
| Florentine calendar | solar | Julian | Medieval | Republic of Florence | Variant of the Julian calendar in use in medieval Florence |
| Pisan calendar | solar | Julian | Medieval | Republic of Pisa | Variant of the Julian calendar in use in medieval Pisa |
| Tamil calendar | solar | Hindu | Ancient | Tamil Nadu | The Hindu calendar used in Tamil Nadu |
| Kollam Era | sidereal solar | Hindu | 825 | Kerala | It is believed that the era was started by the Syrian Christian saints Mar Sabor and Mar Proth who arrived in Kollam in the 9th century CE. This event is recorded in the Kollam Tarisappalli copper plates issued to them. The news of the physical disappearance of Sri Adi Shankaracharya in 820 CE at Kedarnath reached the Malabar coast only a few years later. It is believed that Kerala began the Malayalam era in 825 CE in his memory. According to Hermann Gundert, Kollam era started as part of erecting a new Shiva Temple in Kollam and because of the strictly local and religious background, the other regions did not follow this system at first. Once Kollam port emerged as an important trade center, however, the other principalities also started following the new system of calendar. This theory backs the remarks of Ibn Battuta as well. The Kollam era may also be attributed to the legend of Paraśurāma, an incarnation of Vishnu. It is sometimes divided into cycles of 1,000 years reckoned from 1176 BCE. Thus, 825 CE would have been the first year of the era's third millennium. |
| Nepali calendar | solar | Hindu/ Buddhist | Medieval | Nepal | One of the Hindu calendars |
| Nepal Sambat | lunisolar | Buddhist/ Hindu | 9th century | Nepal | A lunisolar Buddhist calendar traditional to Nepal, recognition in Nepal in 2008. |
| Bengali calendar | lunisolar | Bengali | Medieval | Bengal | Revised in 1987. |
| Thai lunar calendar | lunisolar | Hindu/Buddhist | Medieval | Thailand | A Buddhist calendar |
| Pawukon calendar | fixed (210 days) | Hindu | | Bali | |
| Old Icelandic calendar | solar | | 10th century | medieval Iceland | Partly inspired by the Julian calendar and partly by older Germanic calendar traditions. Leap week calendar based on a year of 364 days. |
| Vietnamese calendar | lunisolar | Chinese-derived | 10th century | Vietnam | After Vietnam regained independence following the third Chinese domination of Vietnam, the following dynasties established their own calendars based on Chinese prototypes, and every subsequent dynasty had appointed officers to man and create the calendar to be used in the realm. |
| Jalali calendar | solar | Iranian | 1079 | Seljuk Sultanate | A calendar reform commissioned by Sultan Jalal al-Din Malik Shah I |
| Hebrew calendar | lunisolar | Babylonian/Seleucid-derived | 11th/12th century | Judaism | Recorded by Maimonides in the Mishneh Torah, resulting from various reforms and traditions developing since Late Antiquity. The Anno Mundi era gradually replaced the Seleucid era in Rabbinical literature in the 11th century. |
| Tibetan calendar | lunisolar | Buddhist/Chinese-derived | 13th century | Tibet | The Kalacakra, a Buddhist calendar introduced in 13th-century Tibet |
| Seasonal Instruction | solar | Chinese | 1281 | China | Based on a solar year of 365.2425 (equal to the Gregorian year) |
| Runic calendar | solar | Julian | 13th century | Sweden | A written representation of the Metonic cycle used in medieval and early modern Sweden, allowing to calculate the dates of the full moons relative to the Julian date. The introduction of the Gregorian calendar in Sweden in 1753 rendered the runic calendars unusable. |
| Six Imperial Calendars (ß) | solar | Chinese | Ming dynasty | China | In use 1368-1644 |
| Incan calendar | lunisolar | Pre-Columbian | 15th century | Inca Empire | |
| Muisca calendar | lunisolar | Pre-Columbian | 15th century | Muisca | Complex lunisolar calendar with three different years, composed of months divided into thirty days. After the Spanish conquest of the Muisca Confederation in present-day central Colombia in 1537 first replaced by the European Julian and as of 1582 the Gregorian calendar. |
| Chula Sakarat | lunisolar | Burmese | 16th century | Southeast Asia | |
| Gregorian calendar | solar | Julian-derived | 1582 | worldwide | Introduced as a reform of the Julian calendar in the Roman Catholic church, since the 20th century in de facto use worldwide. |
| Javanese calendar | lunar | Islamic influenced | 1633 | Java | Based on the Hindu calendar using the Saka era (78 CE), but changed by Sultan Agung of Mataram its method of counting of years from solar years to lunar years as per the Islamic calendar. |
| Seasonal Constitution | solar | Chinese | 1645 | China | First Chinese Calendar to use the true motion of the sun. |
| Swedish calendar | solar | Julian-derived | 1700 | Sweden | Part of the controversy surrounding the adoption of the Gregorian calendar, in use 1700–1712. |
| Astronomical year numbering | solar | Julian-derived | 1740 | Astronomy | A mixture of Julian and Gregorian calendar, giving dates before 1582 in the Julian calendar, and dates after 1582 in the Gregorian calendar, counting 1 BC as year zero, and negative year numbers for 2 BC and earlier. |
| French Republican Calendar | solar | Gregorian | 1793 | First French Republic | In use in revolutionary France 1793 to 1805. |
| Pancronometer | solar | Gregorian | 1745 | — | Universal Georgian Calendar proposed by Hugh Jones |
| Rumi calendar | solar | Julian | 1839 | Ottoman Empire | Julian calendar using the Hijri era introduced in the Ottoman Empire. |
| Positivist calendar | Solar | Gregorian | 1849 | — | Solar calendar with 13 months of 28 days. |
| Badí‘ calendar | solar | Baháʼí | 1873 | Baháʼí | Uses a year of 19 months of 19 days each and a 1844 era. Also known as the "Baháʼí Calendar" or the "Wondrous Calendar". |
| Thai solar calendar | solar | Gregorian | 1888 | Thailand | The Gregorian calendar but using the Buddhist Era (543 BC) |
| Invariable Calendar | solar | Gregorian | 1900 | — | Gregorian calendar with four 91-day quarters of 13 weeks |
| International Fixed Calendar | solar | Gregorian | 1902 | — | A "perpetual calendar" with a year of 13 months of 28 days each. |
| Minguo calendar | solar | Gregorian | 1912 | Republic of China | Months and days use the Gregorian calendar, introduced in China in 1912. |
| Revised Julian calendar | solar | Julian-derived | 1923 | some Orthodox churches | currently synchronized with the Gregorian calendar, but different leap rule and cycle (900 years), also called Meletian calendar or Milanković calendar, after Serbian scientist Milutin Milanković who developed it. |
| Solar Hijri calendar | solar | Iranian/Islamic | 1925 | Iran, Afghanistan | New Year is the day of the astronomical vernal equinox. The calendar as introduced in 1925 revived Iranian month names but counted the years of the Hijri era. The era was changed in 1976 to 559 BC (reign of Cyrus the Great), but was reverted to the Hijri era after the Iranian Revolution. |
| Era Fascista | solar | Gregorian | 1926 | Italy | Epoch is 29 October 1922; in use from 1926–1943 |
| Soviet calendar | solar | Gregorian | 1929 | Soviet Union | Gregorian calendar with 5- and 6-day weeks, used during 1929 to 1940. |
| World Calendar | solar | Gregorian | 1930 | — | Perpetual calendar with 1–2 off-week days, preferred and almost adopted by the United Nations in 1950s |
| Pax Calendar | solar | Gregorian | 1930 | — | Leap week calendar |
| Pataphysical calendar | solar | Gregorian | 1949 | — | Absurdist variant of the Gregorian calendar by Alfred Jarry. |
| Indian national calendar | solar | Gregorian-derived | 1957 | Republic of India | Gregorian calendar with months based in traditional Hindu calendars and numbering years based on the Saka era (AD 78). |
| Assyrian calendar | solar | Babylonian | 1950s | Assyrianism | Solar calendar with an "Assyrian era" of 4750 BC, introduced in Assyrian nationalism in the 1950s |
| Discordian calendar | solar | Gregorian | 1963 | Discordianism | Calendar invented in the context of the absurdist or parody religion of Discordianism, Gregorian calendar variant with a year consisting of five 73-day seasons. |
| World Season Calendar | solar | Gregorian | 1973 | — | Divides the year into four seasons. |
| Dreamspell | solar | Mayan | 1990 | esotericism | 13 months of 28 days each, synchronized with the Maya 260-day Tzolkin, calibrated to the Chilam Balam timing systems |
| Holocene calendar | solar | Gregorian | 1993 | — | The Gregorian calendar with the era shifted by 10,000 years. |
| Juche era calendar | solar | Gregorian | 1997 | North Korea | Gregorian calendar with the era 1912 (birth of Kim Il-sung) |
| Nanakshahi calendar | solar | Sikh | 1789 | Sikhism religion, Punjab | Sikh Calendar numbering years based on the era 1469 (birth of Guru Nanak) |
| Symmetry454 | solar | Gregorian | 2004 | — | Leap week calendar with 4:5:4 weeks per month |
| Hanke–Henry Permanent Calendar | solar | Gregorian | 2004 | — | Leap week calendar with 30:30:31 days per month, revised in 2011 and 2016 |
| Igbo calendar | solar | Indigenous West African | 2009 | Igbo people | Proposal based in Igbo tradition dating back to 13th century, 13 lunar months of 28 days divided into seven 4-day periods, plus leap days. |
| Vira Nirvana Samvat | Lunisolar | Hindu | Ancient India | India/Nepal | The Vira Nirvana Samvat (era) is a calendar era beginning on 7 October 527 BCE. It commemorates the Nirvana of Lord Mahaviraswami, the 24th Jain Tirthankara. This is one of the oldest system of chronological reckoning which is still used in India. |
| Mizo calendar | Lunisolar | Mizo | unknown / Lushai Chiefdoms | Mizo people | 12 month calendar historically used to track the cycle of jhum cultivation and festivals. |

## Variant month names

Regional or historical names for lunations or Julian/Gregorian months
| Tradition | culture | comments |
| Germanic calendar | Germanic | Medieval records of Germanic names of lunar months later equated with the Julian months. |
| Berber calendar | Berber | reconstructed medieval Berber-language names of the Julian months used in pre-Islamic (Roman era) North Africa |
| Lithuanian calendar | Lithuania | Lithuanian names for the Gregorian months and days of the week, officially recognized in 1918. |
| Rapa Nui calendar | Easter Islands | Thirteen names of lunar months recorded in the 19th century. |
| Xhosa calendar | Xhosa people | |
| Turkmen | Turkmenistan | Turkmen names officially adopted in 2002 following Ruhnama by president-for-life Saparmurat Niyazov. |
| Hellenic calendars | Hellenistic Greece | A great variety of regional month names in Ancient Greece, mostly attested in the 2nd century BC. |
| Slavic calendar | Slavic | Local month names in various Slavic countries, based on weather patterns and conditions, and agricultural activities that take place in each respective month. |
| Romanian calendar | Romania and Moldova | Traditional names for the twelve months of the Gregorian calendar, which are usually used by the Romanian Orthodox Church. |
| Thai calendar | Thailand | Names of 12 zodiacs, borrowed from Sanskrit zodiacs. The endings indicates the length of the months. |

## Non-standard weeks

| Tradition | Week Length | Comments |
| Bali | Various | The Balinese calendar has ten types of weeks (wewaran): Ékawara the one-day week, Dwiwara the two-day week, Triwara the three-day week, all the way until Dasawara the ten-day week. |
| Igbo | 4 days | The traditional Igbo week consists of four market days: eke, orie, afor, and nkwo. |
| Yoruba | 4 days | Traditional Yoruba calendar |
| Korea | 5 days | For traditional markets in Korea, for example, the market is open every five days. |
| Java | 5 days | Pasaran, used to determine the opening of markets in Javanese-speaking areas. The days are: Legi, Pahing, Pon, Wagé, and Kliwon. Combined with the regular 7-day week, they make up a 35-day cycle for wetonan, the Javanese astrology used to determine marriage compatibility, luck, personality, etc. |
| Discordian | 5 days | |
| Akan | 6 days | A traditional "six-day week" which combined with the Gregorian seven-day week gave rise to a 42-day cycle. |
| Ancient Rome | 8 days | The Roman nundinal cycle. |
| Burmese | 8 days | |
| Celtic | 8 days | reconstructed. |
| Baltic | 9 days | Linguistic reconstruction; the Gediminas Sceptre indicated that a week lasted for nine days during King Gediminas' reign. |
| Chinese | 10 days | |
| Egyptian Calendar | 10 days | The 10-day period was known as decans or decades |
| French Republican Calendar | 10 days | |
| Aztecs | 13 days | Trecena, division of the Tonalpohualli 260-day period |

## 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 used for accounting
* 365-day calendar used for accounting
* Unix time, number of seconds elapsed since 1 January 1970, 00:00:00 (UTC).
* Julian day, number of days elapsed since 1 January 4713 BC, 12:00:00 (UTC).
* Heliocentric Julian Date, Julian day corrected for differences in the Earth's position with respect to the Sun.
* Barycentric Julian Date, Julian day corrected for differences in the Earth's position with respect to the barycentre of the Solar System.
* Lilian date, 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 (proposed for Mars, not used in planetary science)
* Discworld calendar (fictional)
* Middle-earth calendars (fictional)
* Stardates (from Star Trek, fictional)