A month is a unit of

time Time is the continuous progression of existence that occurs in an apparently irreversible process, irreversible succession from the past, through the present, and into the future. It is a component quantity of various measurements used to sequ ...

, used with

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 calendar date, date is the designation of a single and specific day within such a system. A calendar is ...

s, that is approximately as long as a natural phase cycle of the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

; the words ''month'' and ''Moon'' are

cognate In historical linguistics, cognates or lexical cognates are sets of words that have been inherited in direct descent from an etymological ancestor in a common parent language. Because language change can have radical effects on both the s ...

s. The traditional concept of months arose with the cycle of

Moon phase A lunar phase or Moon phase is the apparent shape of the Moon's directly sunlit portion as viewed from the Earth. Because the Moon is tidally locked with the Earth, the same hemisphere is always facing the Earth. In common usage, the four majo ...

s; such

lunar month In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month. Variations In Shona, Middle Eastern, and Euro ...

s ("lunations") are synodic months and last approximately 29.53

day A day is the time rotation period, period of a full Earth's rotation, rotation of the Earth with respect to the Sun. On average, this is 24 hours (86,400 seconds). As a day passes at a given location it experiences morning, afternoon, evening, ...

s, making for roughly 12.37 such months in one Earth year. From excavated

tally stick A tally stick (or simply a tally) was an ancient memory aid used to record and document numbers, quantities, and messages. Tally sticks first appear as animal bones carved with notches during the Upper Palaeolithic; a notable example is the Is ...

s, researchers have deduced that people counted days in relation to the Moon's phases as early as the

Paleolithic The Paleolithic or Palaeolithic ( years ago) ( ), also called the Old Stone Age (), is a period in human prehistory that is distinguished by the original development of stone tools, and which represents almost the entire period of human prehist ...

age. Synodic months, based on the Moon's

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

with respect to the Earth–Sun line, are still the basis of many calendars today and are used to divide the

year A year is a unit of time based on how long it takes the Earth to orbit the Sun. In scientific use, the tropical year (approximately 365 Synodic day, solar days, 5 hours, 48 minutes, 45 seconds) and the sidereal year (about 20 minutes longer) ...

. Calendars that developed from the

Roman calendar The Roman calendar was the calendar used by the Roman Kingdom and Roman Republic. Although the term is primarily used for Rome's pre-Julian calendars, it is often used inclusively of the Julian calendar established by Julius Caesar in 46&nbs ...

system, such as the internationally used

Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian cale ...

, divide the year into 12 months, each of which lasts between 28 and 31 days. The names of the months were Anglicized from various Latin names and events important to Rome, except for the months 9–12, which are named after the Latin numerals 7–10 (''septem'', ''octo'', ''novem'', and ''decem'') because they were originally the seventh through tenth months in the Roman calendar.

Macrobius Macrobius Ambrosius Theodosius, usually referred to as Macrobius (fl. AD 400), was a Roman provincial who lived during the early fifth century, during late antiquity, the period of time corresponding to the Later Roman Empire, and when Latin was ...

, ''

Saturnalia Saturnalia is an Roman festivals, ancient Roman festival and holiday in honour of the List of Roman deities, god Saturn (mythology), Saturn, held on 17 December in the Julian calendar and later expanded with festivities until 19 December. By t ...

'', tr. Percival Vaughan Davies (New York: Columbia University Press, 1969), book I, chapters 12–13, pp. 89–95. In the modern Gregorian calendar, the only month with a variable number of days is the second month, February, which has 29 days during a

leap year A leap year (also known as an intercalary year or bissextile year) is a calendar year that contains an additional day (or, in the case of a lunisolar calendar, a month) compared to a common year. The 366th day (or 13th month) is added to keep t ...

and 28 days otherwise.

Types of months in astronomy

The following types of months are mainly of significance in astronomy. Most of them (but not the distinction between sidereal and tropical months) were first recognized in Babylonian lunar astronomy. # The sidereal month is defined as the Moon's

in a non-rotating frame of reference (which on average is equal to its

rotation period In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the '' sidereal rotation period'' (or ''sidereal day''), i.e., the time that the objec ...

in the same frame). It is about 27.32166 days (27 days, 7 hours, 43 minutes, 11.6 seconds). It is closely equal to the time it takes the Moon to twice pass a "fixed"

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

(different stars give different results because all have a very small

proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...

and are not really fixed in position). # A synodic month is the most familiar lunar cycle, defined as the time interval between two consecutive occurrences of a particular phase (such as new moon or full moon) as seen by an observer on Earth. The mean length of the synodic month is 29.53059 days (29 days, 12 hours, 44 minutes, 2.8 seconds). Due to the eccentricity of the lunar orbit around Earth (and to a lesser degree, the Earth's elliptical orbit around the Sun), the length of a synodic month can vary by up to seven hours. # The tropical month is the average time for the Moon to pass twice through the same

equinox A solar equinox is a moment in time when the Sun appears directly above the equator, rather than to its north or south. On the day of the equinox, the Sun appears to rise directly east and set directly west. This occurs twice each year, arou ...

point of the sky. It is 27.32158 days, very slightly shorter than the sidereal month (27.32166) days, because of

precession of the equinoxes In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's Rotation around a fixed axis, rotational axis. In the absence of precession, the astronomical body's orbit would show ...

. # An anomalistic month is the average time the Moon takes to go from

perigee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

to perigee—the point in the Moon's orbit when it is closest to Earth. An anomalistic month is about 27.55455 days on average. # The draconic month, draconitic month, or nodal month is the period in which the Moon returns to the same

node In general, a node is a localized swelling (a "knot") or a point of intersection (a vertex). Node may refer to: In mathematics * Vertex (graph theory), a vertex in a mathematical graph *Vertex (geometry), a point where two or more curves, lines ...

of its orbit; the nodes are the two points where the Moon's orbit crosses the plane of the Earth's orbit. Its duration is about 27.21222 days on average. A synodic month is longer than a sidereal month because the Earth-Moon system is orbiting the Sun in the same direction as the Moon is orbiting the Earth. The Sun moves eastward with respect to the stars (as does the Moon) and it takes about 2.2 days longer for the Moon to return to the same apparent position with respect to the Sun. An anomalistic month is longer than a sidereal month because the perigee moves in the same direction as the Moon is orbiting the Earth, one revolution in nine years. Therefore, the Moon takes a little longer to return to perigee than to return to the same star. A draconic month is shorter than a sidereal month because the nodes move in the opposite direction as the Moon is orbiting the Earth, one revolution in 18.6 years. Therefore, the Moon returns to the same node slightly earlier than it returns to the same star.

Calendrical consequences

At the simplest level, most well-known lunar calendars are based on the initial approximation that 2 lunations last 59

solar day A synodic day (or synodic rotation period or solar day) is the period for a celestial object to rotate once in relation to the star it is orbiting, and is the basis of solar time. The synodic day is distinguished from the sidereal day, which is ...

s: a 30-day full month followed by a 29-day hollow month — but this is only roughly accurate and regularly needs intercalation (correction) by a

leap day A leap year (also known as an intercalary year or bissextile year) is a calendar year that contains an additional day (or, in the case of a lunisolar calendar, a month) compared to a common year. The 366th day (or 13th month) is added to kee ...

. Additionally, the synodic month does not fit easily into the solar (or 'tropical') year, which makes accurate, rule-based

lunisolar calendar A lunisolar calendar is a calendar in many cultures, that combines monthly lunar cycles with the solar year. As with all calendars which divide the year into months, there is an additional requirement that the year have a whole number of mont ...

s that combine the two cycles complicated. The most common solution to this problem is the

Metonic cycle The Metonic cycle or enneadecaeteris (from , from ἐννεακαίδεκα, "nineteen") is a period of almost exactly 19 years after which the lunar phases recur at the same time of the year. The recurrence is not perfect, and by precise obser ...

, which takes advantage of the fact that 235 lunations are approximately 19 tropical years (which add up to not quite 6,940 days): 12 years have 12 lunar months, and 7 years are 13 lunar months long. However, a

Metonic calendar The Metonic cycle or enneadecaeteris (from , from ἐννεακαίδεκα, "nineteen") is a period of almost exactly 19 years after which the lunar phases recur at the same time of the year. The recurrence is not perfect, and by precise obser ...

based year will drift against the seasons by about one day every 2 centuries. Metonic calendars include the calendar used in the

Antikythera Mechanism The Antikythera mechanism ( , ) is an Ancient Greece, Ancient Greek hand-powered orrery (model of the Solar System). It is the oldest known example of an Analog computer, analogue computer. It could be used to predict astronomy, astronomical ...

about 21 centuries ago, and the

Hebrew calendar The Hebrew calendar (), also called the Jewish calendar, is a lunisolar calendar used today for Jewish religious observance and as an official calendar of Israel. It determines the dates of Jewish holidays and other rituals, such as '' yahrze ...

. Alternatively in a pure

lunar calendar A lunar calendar is a calendar based on the monthly cycles of the Moon's phases ( synodic months, lunations), in contrast to solar calendars, whose annual cycles are based on the solar year, and lunisolar calendars, whose lunar months are br ...

, years are defined as having always 12 lunations, so a year is 354 or 355 days long: the

Islamic calendar The Hijri calendar (), also known in English as the Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the Ramad ...

is the prime example. Consequently, an Islamic year is about 11 days shorter than a solar year and cycles through the seasons in about 33 solar = 34 lunar years: the

Islamic New Year The Islamic New Year (, '), also called the Hijri New Year, is the day that marks the beginning of a new lunar Hijri year, and is the day on which the year count is incremented. The first day of the Islamic year is observed by most Muslims on ...

has a different

date in each (solar) year. Purely

solar calendar A solar calendar is a calendar whose dates indicates the season or almost equivalently the apparent position of the Sun relative to the stars. The Gregorian calendar, widely accepted as a standard in the world, is an example of a solar calendar ...

s often have months which no longer relate to the phase of the Moon, but are based only on the motion of the Sun relative to the equinoxes and solstices, or are purely conventional like in the widely used

. The complexity required in an accurate lunisolar calendar may explain why solar calendars have generally replaced lunisolar and lunar calendars for civil use in most societies.

Months in various calendars

Beginning of the lunar month

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 ...

, the Hebrew Lunisolar calendar and the

Islamic Lunar calendar Islam is an Abrahamic monotheistic religion based on the Quran, and the teachings of Muhammad. Adherents of Islam are called Muslims, who are estimated to number 2 billion worldwide and are the world's second-largest religious populati ...

started the month with the first appearance of the thin crescent of the

new moon In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar eclipse. ...

. However, the motion of the Moon in its

orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

is very complicated and its period is not constant. The date and time of this actual observation depends on the exact geographical longitude as well as latitude, atmospheric conditions, the visual acuity of the observers, etc. Therefore, the beginning and lengths of months defined by observation cannot be accurately predicted. While some like orthodox Islam and the Jewish Karaites still rely on actual moon observations, reliance on astronomical calculations and tabular methods is increasingly common in practice.

Ahom calendar

There are 12 months and an additional leap year month in the Ahom sexagenary calendar known as Lak-ni. The first month is Duin Shing.

Roman calendar

The

was reformed several times, the last three enduring reforms during historical times. The last three reformed Roman calendars are called the ''Julian'', ''Augustan'', and ''Gregorian''; all had the same number of days in their months. Despite other attempts, the names of the months after the Augustan calendar reform have persisted, and the number of days in each month (except February) have remained constant since before the Julian reform. The

, like the Roman calendars before it, has twelve months, whose

Anglicized Anglicisation or anglicization is a form of cultural assimilation whereby something non-English becomes assimilated into or influenced by the culture of England. It can be sociocultural, in which a non-English place adopts the English language ...

names are: : The famous

mnemonic A mnemonic device ( ), memory trick or memory device is any learning technique that aids information retention or retrieval in the human memory, often by associating the information with something that is easier to remember. It makes use of e ...

'' Thirty days hath September'' is a common way of teaching the lengths of the months in the English-speaking world. The knuckles of the four fingers of one's hand and the spaces between them can be used to remember the lengths of the months. By making a fist, each month will be listed as one proceeds across the hand. All months landing on a knuckle are 31 days long and those landing between them are 30 days long, with variable February being the remembered exception. When the knuckle of the index finger is reached (July), go over to the first knuckle on the other fist, held next to the first (or go back to the first knuckle) and continue with August. This physical mnemonic has been taught to primary school students for many decades, if not centuries. This cyclical pattern of month lengths matches the

musical keyboard A musical keyboard is the set of adjacent depressible levers or keys on a musical instrument. Keyboards typically contain keys for playing the twelve notes of the Western musical scale, with a combination of larger, longer keys and smaller, sho ...

alternation of wide white keys (31 days) and narrow black keys (30 days). The note F corresponds to January, the note F corresponds to February, the exceptional 28–29 day month, and so on.

Numerical relations

The mean month-length in the Gregorian calendar is 30.436875 days. Any five consecutive months that do not include February contain 153 days.

Calends, nones, and ides

Months in the pre-Julian

included: * ''

Intercalaris Mercedonius (Latin for "Work Month"),. also known as Mercedinus, Interkalaris or Intercalaris (), was the intercalary month of the Roman calendar. The resulting leap year was either 377 or 378 days long. It theoretically occurred every two (or occ ...

'' an

intercalary month Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of days or months. Solar ca ...

occasionally embedded into February, to realign the calendar. * ''

Quintilis In the ancient Roman calendar, Quintilis or Quinctilis was the month following Junius (June) and preceding Sextilis (August). ''Quintilis'' is Latin for "fifth": it was the fifth month (''quintilis mensis'') in the earliest calendar attributed t ...

'', later renamed to ''Julius'' in honour of

Julius Caesar Gaius Julius Caesar (12 or 13 July 100 BC – 15 March 44 BC) was a Roman general and statesman. A member of the First Triumvirate, Caesar led the Roman armies in the Gallic Wars before defeating his political rival Pompey in Caesar's civil wa ...

. * ''

Sextilis Sextilis () or ''mensis Sextilis'' was the Latin name for what was originally the sixth month in the Roman calendar The Roman calendar was the calendar used by the Roman Kingdom and Roman Republic. Although the term is primarily used for ...

'', later renamed to ''Augustus'' in honour of

Augustus Gaius Julius Caesar Augustus (born Gaius Octavius; 23 September 63 BC – 19 August AD 14), also known as Octavian (), was the founder of the Roman Empire, who reigned as the first Roman emperor from 27 BC until his death in A ...

. The Romans divided their months into three parts, which they called the ''calends'', the ''nones'', and the ''ides''. Their system is somewhat intricate. The ides occur on the thirteenth day in eight of the months, but in March, May, July, and October, they occur on the fifteenth. The nones always occur 8 days (one Roman 'week') before the ides, i.e., on the fifth or the seventh. The

calends The calends or kalends () is the first day of every month in the Roman calendar. The English word "calendar" is derived from this word. Use The Romans called the first day of every month the ''calends'', signifying the start of a new lunar pha ...

are always the first day of the month, and before Julius Caesar's reform fell sixteen days (two Roman weeks) after the ides (except the ides of February and the intercalary month).

Relations between dates, weekdays, and months in the Gregorian calendar

Within a month, the following dates fall on the same day of the week: * 01, 08, 15, 22, and 29 (e.g., in January 2022, all these dates fell on a Saturday) * 02, 09, 16, 23, and 30 (e.g., in January 2022, all these dates fell on a Sunday) * 03, 10, 17, 24, and 31 (e.g., in January 2022, all these dates fell on a Monday) * 04, 11, 18, and 25 (e.g., in January 2022, all these dates fell on a Tuesday) * 05, 12, 19, and 26 (e.g., in January 2022, all these dates fell on a Wednesday) * 06, 13, 20, and 27 (e.g., in January 2022, all these dates fell on a Thursday) * 07, 14, 21, and 28 (e.g., in January 2022, all these dates fell on a Friday) Some months have the same date/weekday structure. In a non-leap year: * January/October (e.g., in 2022, they began on a Saturday) * February/March/November (e.g., in 2022, they began on a Tuesday) * April/July (e.g., in 2022, they began on a Friday) * September/December (e.g., in 2022, they began on a Thursday) * 1 January and 31 December fall on the same weekday (e.g. in 2022 on a Saturday) In a leap year: * February/August (e.g., in 2020, they began on a Saturday) * March/November (e.g., in 2020, they began on a Sunday) * January/April/July (e.g., in 2020, they began on a Wednesday) * September/December (e.g., in 2020, they began on a Tuesday) * 29 February (the leap day) falls on the same weekday like 1, 8, 15, 22 February and 1 August (see above; e.g. in 2020 on a Saturday)

Hebrew calendar

The

has 12 or 13 months. #

Nisan Nisan (or Nissan; from ) in the Babylonian and Hebrew calendars is the month of the barley ripening and first month of spring. The name of the month is an Akkadian language borrowing, although it ultimately originates in Sumerian ''nisag' ...

, 30 days ניסן #

Iyar Iyar (Hebrew language, Hebrew: or , Hebrew language#Modern Hebrew, Standard ''ʾĪyyar'' Tiberian vocalization, Tiberian ''ʾĪyyār''; from "Rosette (design), rosette; blossom") is the eighth month of the civil year (which starts on 1 Tishrei ...

, 30 days אייר #

Sivan ''Sivan'' (, from Akkadian ''simānu'', meaning "season; time") is the ninth month of the civil year and the third month of the religious year on the Hebrew calendar. It is a month of 30 days. ''Sivan'' usually falls in May–June on the Grego ...

, 30 days סיון # Tammuz, 29 days תמוז # Av, 30 days אב #

Elul Elul (Hebrew language, Hebrew: , Hebrew language#Modern Hebrew, Standard , Tiberian vocalization, Tiberian ) is the twelfth month of the civil year and the sixth month of the Jewish religious year, religious year in the Hebrew calendar. It is a m ...

, 29 days אלול #

Tishri Tishrei () or Tishri (; ''tīšrē'' or ''tīšrī''; from Akkadian language, Akkadian ''tašrītu'' "beginning", from ''šurrû'' "to begin") is the first month of the civil year (which starts on 1 Tishrei) and the seventh month of the eccles ...

, 30 days תשרי # Marcheshvan, 29/30 days מַרְחֶשְׁוָן #

Kislev Kislev or Chislev (Hebrew language, Hebrew: , Hebrew language#Modern Hebrew, Standard ''Kīslev'' Tiberian vocalization, Tiberian ''Kīslēw''), is the third month of the civil year and the ninth month of the ecclesiastical year on the Hebrew c ...

, 30/29 days כסלו #

Tevet Tevet (Hebrew: , ''Ṭevet''; ; from Akkadian ) is the fourth month of the civil year and the tenth month of the ecclesiastical year on the Hebrew calendar. It follows Kislev and precedes Shevat. It is a month of 29 days. Tevet usually occurs ...

, 29 days טבת #

Shevat Shevat (, , ; from ) is the fifth month of the civil year starting in Tishre (or Tishri) and the eleventh month of the ecclesiastical year on the Hebrew calendar starting in Nisan. It is a month of 30 days. Shevat usually occurs in January– ...

, 30 days שבט # Adar 1, 30 days,

intercalary Intercalation may refer to: *Intercalation (chemistry), insertion of a molecule (or ion) into layered solids such as graphite *Intercalation (timekeeping), insertion of a leap day, week or month into some calendar years to make the calendar follo ...

month אדר א # Adar 2, 29 days אדר ב Adar 1 is only added 7 times in 19 years. In ordinary years, Adar 2 is simply called Adar.

Islamic calendar

There are also twelve months in the Islamic calendar. They are named as follows: #

Muharram Al-Muharram () is the first month of the Islamic calendar. It is one of the four sacred months of the year when warfare is banned. It precedes the month of Safar. The tenth of Muharram is known as Ashura, an important day of commemoration in ...

(Restricted/sacred) محرّم #

Safar Safar (), also spelt as Safer in Turkish, is the second month of the lunar Islamic calendar. Most of the Islamic months were named according to ancient Sabean/Sabaic weather conditions; however, since the calendar is lunar, the months shift ...

(Empty/Yellow) صفر # Rabī' al-Awwal/Rabi' I (First Spring) ربيع الأول # Rabī' ath-Thānī/Rabi' al-Aakhir/Rabi' II (Second spring or Last spring) ربيع الآخر أو ربيع الثاني # Jumada al-Awwal/Jumaada I (First Freeze) جمادى الأول # Jumada ath-Thānī or Jumādā al-Thānī/Jumādā II (Second Freeze or Last Freeze) جمادى الآخر أو جمادى الثاني #

Rajab Rajab () is the seventh month of the Islamic calendar. The lexical definition of the classical Arabic verb ''rajaba'' is "to respect", which could also mean "be awe or be in fear", of which Rajab is a derivative. This month is regarded as one ...

(To Respect) رجب # Sha'bān (To Spread and Distribute) شعبان # Ramadān (Parched Thirst) رمضان # Shawwāl (To Be Light and Vigorous) شوّال #

Dhu al-Qi'dah Dhu al-Qa'dah (, ', ), also spelled Dhu al-Qi'dah or Zu al-Qa'dah, is the eleventh month in the Islamic calendar. It could possibly mean "possessor or owner of the sitting and seating place" - the space occupied while sitting or the manner of t ...

(The Master of Truce) ذو القعدة #

Dhu al-Hijjah Dhu al-Hijjah (also Dhu al-Hijja ) is the twelfth and final month in the Islamic calendar. Being one of the four sacred months during which war is forbidden, it is the month in which the '' Ḥajj'' () takes place as well as Eid al-Adha (). T ...

(The Possessor of Hajj) ذو الحجة See

for more information on the Islamic calendar.

Arabic calendar

Hindu calendar

The

Hindu calendar The Hindu calendar, also called Panchangam, Panchanga (), is one of various lunisolar calendars that are traditionally used in the Indian subcontinent and Southeast Asia, with further regional variations for social and Hindu religious purposes ...

has various systems of naming the months. The months in the lunar calendar are: These are also the names used in the

Indian national calendar The Indian national calendar, also called the Shaka calendar or Śaka calendar, is a solar calendar that is used alongside the Gregorian calendar by ''The Gazette of India'', in news broadcasts by All India Radio, and in calendars and officia ...

for the newly redefined months. Purushottam Maas or Adhik Maas ( translit. ' = 'extra', ' = 'month') is an extra month in the

that is inserted to keep the

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

s aligned. "Purushottam" is an epithet of

Vishnu Vishnu (; , , ), also known as Narayana and Hari, is one of the Hindu deities, principal deities of Hinduism. He is the supreme being within Vaishnavism, one of the major traditions within contemporary Hinduism, and the god of preservation ( ...

, to whom the month is dedicated. The names in the solar calendar are just the names of the

zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south celestial latitude of the ecliptic – the apparent path of the Sun across the celestial sphere over the course of the year. Within this zodiac ...

Mesha King Mesha (Moabite language, Moabite: , vocalized as: ; Hebrew: מֵישַׁע ''Mēšaʿ'') was a king of Moab in the 9th century BC, known most famously for having the Mesha Stele inscribed and erected at Dhiban, Dibon, Jordan. In this inscrip ...

# Vrishabha #

Mithuna ''Maithuna'' (Devanagari: मैथुन) is a Sanskrit term for sexual intercourse within Tantra (Tantric sex), or alternatively for the sexual fluids generated or the couple participating in the ritual. It is the most important of the Panchama ...

# Kataka # Simha # Kanyaa # Tulaa # Vrishcika # Dhanus #

Makara Makara () is a legendary sea-creature in Hindu mythology. In Hindu astrology, Makara is equivalent to the Zodiac sign Capricorn. Makara appears as the vahana (vehicle) of the river goddess Ganga, Narmada, and of the god of the ocean, Varun ...

Kumbha A kumbha () is a type of pottery in India. Traditionally, it is made by Kumbhars, also known as ''Prajapati''s. In the context of Hindu, Jain and Buddhist mythology, the kumbha symbolises the womb. It represents fertility, life, generative ...

# Miina

Baháʼí calendar

The

Baháʼí calendar The Baháʼí calendar used in the Baháʼí Faith is a solar calendar consisting of nineteen months and four or five intercalary days, with new year at the moment of Northern spring equinox. Each month is named after a virtue (''e.g.'', Perfect ...

is the calendar used by the

Baháʼí Faith The Baháʼí Faith is a religion founded in the 19th century that teaches the Baháʼí Faith and the unity of religion, essential worth of all religions and Baháʼí Faith and the unity of humanity, the unity of all people. Established by ...

. It is a solar calendar with regular years of 365 days, and

s of 366 days. Years are composed of 19 months of 19 days each (361 days), plus an extra period of "

Intercalary Days Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of days or months. Solar ca ...

" (4 in regular and 5 in leap years). The months are named after the attributes of God. Days of the year begin and end at sundown.

Iranian calendar (Persian calendar)

The Iranian / Persian calendar, currently used in

Iran Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the nort ...

, also has 12 months. The

Persian Persian may refer to: * People and things from Iran, historically called ''Persia'' in the English language ** Persians, the majority ethnic group in Iran, not to be conflated with the Iranic peoples ** Persian language, an Iranian language of the ...

names are included in the parentheses. It begins on the northern Spring equinox. #

Farvardin Farvardin (, ) is the Iranian Persian name for the first month of the Solar Hijri calendar, the official calendar of Iran, and corresponds with Aries on the Zodiac. Farvardin has thirty-one days. It is the first month of the spring season (''B ...

(31 days, فروردین) # Ordibehesht (31 days, اردیبهشت) # Khordad (31 days, خرداد) # Tir (31 days, تیر) # Mordad (31 days, مرداد) #

Shahrivar Shahrivar (, ) is the sixth month of the Solar Hijri calendar, the official calendar of Iran and Afghanistan. Shahrivar has thirty-one days. It begins in August and ends in September by the Gregorian calendar. The Afghan Persian name is Sonbol ...

(31 days, شهریور) # Mehr (30 days, مهر) #

Aban Apas (, ) is the Avestan language term for "the waters", which, in its innumerable aggregate states, is represented by the Apas, the hypostases of the waters. ''Āb'' (plural ''Ābān'') is the Middle Persian-language form. Introduction "To t ...

(30 days, آبان) #

Azar Azar (, ) is the ninth month of the Solar Hijri calendar, the official calendar of Iran and Afghanistan. Azar has thirty days. It begins in November and ends in December by the Gregorian calendar. Azar corresponds to the Tropical Astrological mon ...

(30 days, آذر) #

Dey Dey (, from ) was the title given to the rulers of the regencies of Algiers, Tripolitania,Bertarelli (1929), p. 203. and Tunis under the Ottoman Empire from 1671 onwards. Twenty-nine ''deys'' held office from the establishment of the deylicate ...

(30 days, دی) #

Bahman Bahman (, ) is the eleventh and penultimate month of the Solar Hijri calendar, the official calendar of Iran and Afghanistan. Bahman has thirty days. It begins in January and ends in February of the Gregorian calendar. The month is equivalent to ...

(30 days, بهمن) #

Esfand Esfand (, ) is the twelfth and final month of the Solar Hijri calendar, the official calendar of Iran and Afghanistan. Esfand has twenty-nine days normally, and thirty during leap years. It begins in February and ends in March of the Gregorian c ...

(29 days- 30 days in leap year, اسفند)

Reformed Bengali calendar

The

Bengali calendar The Bengali Calendar or Bangla Calendar (, colloquially , or , , "Bangla Year") is a solar calendar used in the Bengal region of the Indian subcontinent. In contrast to the traditional Indian Hindu calendar, which begins with the month Chait ...

, used in

Bangladesh Bangladesh, officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world and among the List of countries and dependencies by ...

, follows solar months and it has six seasons. The months and seasons in the calendar are:

Nanakshahi calendar

The months in the

Nanakshahi calendar The Nanakshahi calendar () is a tropical solar calendar used in Sikhism. It is based on the " Barah Maha" (Twelve Months), a composition composed by the Sikh gurus reflecting the changes in nature conveyed in the twelve-month cycle of the year. T ...

are:

Khmer calendar

Different from the Hindu calendar, the Khmer calendar consists of both a lunar calendar and a solar calendar. The solar is used more commonly than the lunar calendar. The Khmer lunar calendar most often contains 12 months; however, the eighth month is repeated (as a "leap month") every two or three years, making 13 months instead of 12. Each lunar month has 29 or 30 days. The year normally has then 354 or 384 days (when an intercalary month is added), but the calendar follows the rules of the Gregorian calendar to determine leap years and add a lead day to one month, so the Khmer lunar year may have a total of 354, 355, 384 or 385 days.

Thai calendar

Tongan calendar

The Tongan calendar is based on the cycles of the Moon around the Earth in one year. The months are: # Liha Mu'a # Liha Mui # Vai Mu'a # Vai Mui # Faka'afu Mo'ui # Faka'afu Mate # Hilinga Kelekele # Hilinga Mea'a # 'Ao'ao # Fu'ufu'unekinanga # 'Uluenga # Tanumanga # 'O'oamofanongo

Pingelapese

Pingelapese The Pingelapese language is a Micronesian language native to Pingelap, an atoll belonging to the state of Pohnpei in the Federated States of Micronesia. This atoll is the homeland to the Pingelapese people, consisting of a three-square mile range ...

, a language from

Micronesia Micronesia (, ) is a subregion of Oceania, consisting of approximately 2,000 small islands in the Northwestern Pacific Ocean. It has a close shared cultural history with three other island regions: Maritime Southeast Asia to the west, Poly ...

, also uses a lunar calendar. There are 12 months associated with their calendar. The Moon first appears in March, they name this month ''Kahlek''. This system has been used for hundreds of years and throughout many generations. This calendar is cyclical and relies on the position and shape of the Moon.

Kollam era (
Malayalam Malayalam (; , ) is a Dravidian languages, Dravidian language spoken in the Indian state of Kerala and the union territories of Lakshadweep and Puducherry (union territory), Puducherry (Mahé district) by the Malayali people. It is one of ...
) calendar

Sinhalese calendar

The Sinhalese calendar is the

Buddhist calendar The Buddhist calendar is a set of lunisolar calendars primarily used in Tibet, Cambodia, Laos, Myanmar, Bangladesh, India, Sri Lanka, Thailand and Vietnam as well as in Malaysia and Singapore and by Chinese populations for religious or o ...

Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

with Sinhala names. Each full moon

Poya Poya is the name given to the lunar month, Lunar monthly Buddhism, Buddhist holiday of Uposatha in Sri Lanka, where it is a civil and bank holiday. When earth makes Full Orbit of moon is normally considered as the poya day in Sri Lanka every mon ...

day marks the start of a Buddhist lunar month. The first month is Bak. # Duruthu (දුරුතු) # Navam (නවම්) # Mædin (මැදින්) # Bak (බක්) # Vesak (වෙසක්) # Poson (පොසොන්) # Æsala (ඇසල) # Nikini (නිකිණි) # Binara (බිනර) # Vap (වප්) # Il (iL) (ඉල්) # Unduvap (උඳුවප්)

Germanic calendar

The old Icelandic calendar is not in official use anymore, but some Icelandic holidays and annual feasts are still calculated from it. It has 12 months, broken down into two groups of six often termed "winter months" and "summer months". The calendar is peculiar in that the months always start on the same

weekday The weekdays and weekend are the complementary parts of the week, devoted to labour and rest, respectively. The legal weekdays (British English), or workweek (American English), is the part of the seven-day week devoted to working. In most o ...

rather than on the same date. Hence Þorri always starts on a Friday sometime between January 22 and January 28 ''(

Old style Old Style (O.S.) and New Style (N.S.) indicate dating systems before and after a calendar change, respectively. Usually, they refer to the change from the Julian calendar to the Gregorian calendar as enacted in various European countries betwe ...

: January 9 to January 15)'', Góa always starts on a Sunday between February 21 and February 27 ''(

: February 8 to February 14)''. * Skammdegi ("Short days") # Gormánuður (mid-October – mid-November, "slaughter month" or " Gór's month") # Ýlir (mid-November – mid-December, "

Yule Yule is a winter festival historically observed by the Germanic peoples that was incorporated into Christmas during the Christianisation of the Germanic peoples. In present times adherents of some new religious movements (such as Modern ...

month") # Mörsugur (mid-December – mid-January, "fat sucking month") # Þorri (mid-January – mid-February, "frozen snow month") # Góa (mid-February – mid-March, "Góa's month, see

Nór Nór (Old Norse Nórr) is according to the Orkneyinga Saga the eponymous founder of Norway. Icelandic accounts Source material Nór of Norway appears in “Fundinn Nóregr” (‘Norway Founded’), hereafter called F, which begins the ''Orkney ...

") # Einmánuður (mid-March – mid-April, "lone" or "single month") * Náttleysi ("Nightless days") # Harpa (mid-April – mid-May, Harpa is a female name, probably a forgotten goddess, first day of Harpa is celebrated as Sumardagurinn fyrsti – first day of summer) # Skerpla (mid-May – mid-June, another forgotten goddess) # Sólmánuður (mid-June – mid-July, "

sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

month") # Heyannir (mid-July – mid-August, "

hay Hay is grass, legumes, or other herbaceous plants that have been cut and dried to be stored for use as animal fodder, either for large grazing animals raised as livestock, such as cattle, horses, goats, and sheep, or for smaller domesticate ...

business month") # Tvímánuður (mid-August – mid-September, "two" or "second month") # Haustmánuður (mid-September – mid-October, "autumn month")

Old Georgian calendar

*NOTE: ''New Year in ancient

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

started from September.''

Old Swedish calendar

# Torsmånad (January, 'Torre's month' (ancient god)) # Göjemånad (February, 'Goe's month' (ancient goddess)) # Vårmånad (March, 'Spring month') # Gräsmånad (April, 'Grass month') # Blomstermånad (May, 'Bloom month') # Sommarmånad (June, 'Summer month') # Hömånad (July, 'Hay month') # Skördemånad, Rötmånad (August, 'Harvest month' or 'Rot month') # Höstmånad (September, 'Autumn month') # Slaktmånad (October, 'Slaughter month') # Vintermånad (November, 'Winter month') # Julmånad (December, 'Christmas month')

Old English calendar

Like the Old Norse calendar, the

Anglo-Saxons The Anglo-Saxons, in some contexts simply called Saxons or the English, were a Cultural identity, cultural group who spoke Old English and inhabited much of what is now England and south-eastern Scotland in the Early Middle Ages. They traced t ...

had their own calendar before they were

Christianized Christianization (or Christianisation) is a term for the specific type of change that occurs when someone or something has been or is being converted to Christianity. Christianization has, for the most part, spread through missions by individu ...

which reflected native traditions and deities. These months were attested by

Bede Bede (; ; 672/326 May 735), also known as Saint Bede, Bede of Jarrow, the Venerable Bede, and Bede the Venerable (), was an English monk, author and scholar. He was one of the most known writers during the Early Middle Ages, and his most f ...

in his works ''On Chronology'' and ''

The Reckoning of Time ''The Reckoning of Time'' (, CPL 2320) is an English era treatise written in Medieval Latin by the Northumbrian monk Bede in 725. Background In mid-7th-century Anglo-Saxon England, there was a desire to see the Easter season less closel ...

'' written in the 8th century. His

Old English Old English ( or , or ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the Early Middle Ages. It developed from the languages brought to Great Britain by Anglo-S ...

month names are probably written as pronounced in Bede's native

Northumbrian dialect Northumbrian dialect or Northumbrian English is any one of several traditional English dialects spoken in the historic counties of Northumberland and County Durham. The term ''Northumbrian'' can refer to the region of Northumbria but can also ...

. The months were named after the Moon; the new moon marking the end of an old month and start of a new month; the full moon occurring in the middle of the month, after which the whole month took its name. : When an

month was needed, a third ''Litha'' month was inserted in mid-summer.

Old Celtic calendar

The

Coligny calendar The Coligny calendar is a bronze plaque with an inscribed calendar, made in Roman Gaul in the 2nd century CE. It lays out a five-year cycle of a lunisolar calendar, each year with twelve lunar months. An intercalary month is inserted before eac ...

(Gaulish/Celtic) is an Iron Age Metonic lunisolar calendar, with 12 lunar months of either 29 or 30 days. The lunar month is calculated to a precision of within 24 hours of the lunar phase, achieved by a particular arrangement of months, and the month of EQUOS having a variable length of 29 or 30 days to adjust for any lunar slippage. This setup means the calendar could stay precisely aligned to its lunar phase indefinitely. The lunar month is divided into two halves, the first of 15 days and the second of 14 or 15 days. The month is calculated to start at the first quarter moon, with the full moon at the centre of the first half-month and the dark moon at the centre of the second half-month. The calendar does not rely on unreliable visual sightings. An intercalary lunar month is inserted before every 30 lunar months to keep in sync with the solar year. Every 276 years this adds one day to the solar point, so if for example the calendar was 1,000 years old, it would only have slipped by less than 4 days against the solar year.

Old Hungarian calendar

Nagyszombati kalendárium (in Latin: ''Calendarium Tyrnaviense'') from 1579. Historically Hungary used a 12-month calendar that appears to have been zodiacal in nature but eventually came to correspond to the Gregorian months as shown below: # Boldogasszony hava (January, 'month of the happy/blessed lady') # Böjtelő hava (February, 'month of early fasting/Lent' or 'month before fasting/Lent') # Böjtmás hava (March, 'second month of fasting/Lent') # Szent György hava (April, 'Saint George's month') # Pünkösd hava (May, 'Pentecost month') # Szent Iván hava (June, 'Saint John he Baptists month') # Szent Jakab hava (July, 'Saint James' month') # Kisasszony hava (August, 'month of the

Virgin Virginity is a social construct that denotes the state of a person who has never engaged in sexual intercourse. As it is not an objective term with an operational definition, social definitions of what constitutes virginity, or the lack thereof ...

') # Szent Mihály hava (September, 'Saint Michael's month') # Mindszent hava (October, 'all saints' month') # Szent András hava (November, 'Saint Andrew's month') # Karácsony hava (December, 'month of Yule/Christmas')

Czech calendar

# Leden – derives from 'led' (ice) # Únor – derives from 'nořit' (to dive, referring to the ice sinking into the water due to melting) # Březen – derives from 'bříza' (birch) # Duben – derives from 'dub' (oak) # Květen – derives from 'květ' (flower) # Červen – derives from 'červená' (red – for the color of apples and tomatoes) # Červenec – is the second 'červen' (formerly known as 2nd červen) # Srpen – derives from old Czech word 'sirpsti' (meaning to reflect, referring to the shine on the wheat) # Září – means 'to shine' # Říjen – derives from 'jelení říje', which refers to the

estrous cycle The estrous cycle (, originally ) is a set of recurring physiological changes induced by reproductive hormones in females of mammalian subclass Theria. Estrous cycles start after sexual maturity in females and are interrupted by anestrous phase ...

of female elk # Listopad – falling leaves # Prosinec – derives from old Czech 'prosiněti', which means to shine through (refers to the sun light shining through the clouds)

Old Egyptian calendar

The ancient civil Egyptian calendar had a year that was 365 days long and was divided into 12 months of 30 days each, plus 5 extra days (epagomenes) at the end of the year. The months were divided into 3 "weeks" of ten days each. Because the ancient Egyptian year was almost a quarter of a day shorter than the solar year and stellar events "wandered" through the calendar, it is referred to as Annus Vagus or "Wandering Year". #Thout #Paopi #Hathor #Koiak #Tooba #Emshir #Paremhat #Paremoude #Pashons #Paoni #Epip #Mesori

Nisga'a calendar

The

Nisga'a The Nisga’a (; ), formerly spelled Nishga or Niska, are an Indigenous people in British Columbia, Canada. They reside in the Nass River valley of northwestern British Columbia. The origin of the term ''Niska'' is uncertain. The spelling ' ...

calendar coincides with the Gregorian calendar with each month referring to the type of harvesting that is done during the month. #K'aliiyee = Going North – referring to the Sun returning to its usual place in the sky #Buxwlaks = Needles Blowing About – February is usually a very windy month in the Nass River Valley #Xsaak = To Eat Oolichans – Oolichans are harvested during this month #Mmaal = Canoes – The river has defrosted, hence canoes are used once more #Yansa'alt = Leaves are Blooming – Warm weather has arrived and leaves on the trees begin to bloom #Miso'o = Sockeye – majority of Sockeye Salmon runs begin this month #Maa'y = Berries – berry picking season #Wii Hoon = Great Salmon – referring to the abundance of Salmon that are now running #Genuugwwikw = Trail of the Marmot – Marmots, Ermines and animals as such are hunted #Xlaaxw = To Eat Trout – trout are mostly eaten this time of year #Gwilatkw = To Blanket – The earth is "blanketed" with snow #Luut'aa = Sit In – the Sun "sits" in one spot for a period of time

French Republican calendar

This calendar was proposed during the French Revolution, and used by the French government for about twelve years from late 1793. There were twelve months of 30 days each, grouped into three ten-day weeks called ''décades''. The five or six extra days needed to approximate the tropical year were placed after the months at the end of each year. A period of four years ending on a leap day was to be called a ''Franciade''. It began at the autumn equinox: * Autumn: #

Vendémiaire Vendémiaire () was the first month in the French Republican calendar. The month was named after the Occitan word ''vendemiaire'' 'grape harvester'. Vendémiaire was the first month of the autumn quarter (''mois d'automne''). It started on the d ...

Brumaire Brumaire () was the second month in the French Republican calendar. The month was named after the French 'fog', which occurs frequently in France at that time of the year. Brumaire was the second month of the autumn quarter (''mois d'automne ...

Frimaire Frimaire () was the third month in the French Republican calendar. The month was named after the French word ''frimas'' 'frost'. Frimaire was the third month of the autumn quarter (''mois d'automne''). It started between 21 November and 23 Novem ...

* Winter: #

Nivôse Nivôse (; also ''Nivose'') was the fourth month in the French Republican Calendar. The month was named after the Latin word ''nivosus'' 'snowy'. Nivôse was the first month of the winter quarter (''mois d'hiver''). It started between 21 and 23 ...

Pluviôse Pluviôse (; also ''Pluviose'') was the fifth month in the French Republican Calendar. The month was named after the Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European langua ...

Ventôse Ventôse (; also ''Ventose'') was the sixth month in the French Republican Calendar. The month was named after the Latin word ''ventosus'' 'windy'. Ventôse was the third month of the winter quarter (''mois d'hiver''). It started between 19 an ...

* Spring: # Germinal #

Floréal Floréal () was the eighth month in the French Republican calendar. The month was named after the Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was or ...

Prairial Prairial () was the ninth month A month is a unit of time, used with calendars, that is approximately as long as a natural phase cycle of the Moon; the words ''month'' and ''Moon'' are cognates. The traditional concept of months arose with the ...

* Summer: #

Messidor Messidor () was the tenth month in the French Republican Calendar. The month was named after the Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was origin ...

Thermidor Thermidor () was the eleventh month in the French Republican calendar. The month was named after the French word ''thermal'', derived from the Greek word ''thermos'' 'heat'. Thermidor was the second month of the summer quarter (''mois d'été ...

Fructidor Fructidor () is the twelfth month in the French Republican Calendar. The month was named after the Latin word ''fructus'' 'fruit'. Fructidor is the third month of the summer quarter (''mois d'été''). By the Gregorian calendar, Fructidor starts ...

Eastern Ojibwe calendar

Ojibwe The Ojibwe (; Ojibwe writing systems#Ojibwe syllabics, syll.: ᐅᒋᐺ; plural: ''Ojibweg'' ᐅᒋᐺᒃ) are an Anishinaabe people whose homeland (''Ojibwewaki'' ᐅᒋᐺᐘᑭ) covers much of the Great Lakes region and the Great Plains, n ...

month names are based on the key feature of the month. Consequently, months between various regions have different names based on the key feature of each month in their particular region. In the Eastern Ojibwe, this can be seen in when the sucker makes its run, which allows the Ojibwe to fish for them. Additionally, Rhodes also informs of not only the variability in the month names, but how in Eastern Ojibwe these names were originally applied to the

s the Ojibwe originally used, which was a

, fixed by the date of ''Akiinaaniwan'' (typically December 27) that marks when sunrise is the latest in the Northern Hemisphere. :

Footnotes

References

Sources

* * * * {{Authority control Calendars Orbit of the Moon Orders of magnitude (time) Units of time