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A month is a unit of time, used with calendars, that is approximately as long as a natural orbital period of the Moon; the words month and Moon are cognates. The traditional concept of months arose with the cycle of Moon phases; such lunar months ("lunations") are synodic months and last approximately 29.53 days, making for roughly 12.37 such months in one Earth year. From excavated tally sticks, researchers have deduced that people counted days in relation to the Moon's phases as early as the Paleolithic age. Synodic months, based on the Moon's orbital period with respect to the Earth–Sun line, are still the basis of many calendars today and are used to divide the year.


Calendars, such as the internationally used Gregorian calendar, that developed from the Roman calendar system 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. [1] 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 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.

  1. The sidereal month is defined as the Moon's orbital period in a non-rotating frame of reference (which on average is equal to its rotation period 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 (different stars give different results because all have a very small proper motion and are not really fixed in position).
  2. 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.
  3. The tropical month is the average time for the Moon to pass twice through the same equinox 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.
  4. An anomalistic month is the average time the Moon takes to go from perigee 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.
  5. The draconic month, draconitic month, or nodal month is the period in which the Moon returns to the same node 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.[ citation needed ] 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 days: 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.

Additionally, the synodic month does not fit easily into the solar (or 'tropical') year, which makes accurate, rule-based lunisolar calendars that combine the two cycles complicated. The most common solution to this problem is the Metonic cycle, 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 based year will drift against the seasons by about one day every 2 centuries. Metonic calendars include the calendar used in the Antikythera Mechanism about 21 centuries ago, and the Hebrew calendar.

Alternatively in a pure lunar calendar, years are defined as having always 12 lunations, so a year is 354 or 355 days long: the Islamic calendar 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 has a different Gregorian calendar date in each (solar) year.

Purely solar calendars 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 Gregorian calendar.

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, the Hebrew Lunisolar calendar and the Islamic Lunar calendar started the month with the first appearance of the thin crescent of the new moon.

However, the motion of the Moon in its orbit 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. [2] [3]

Ahom Calendar

There are 12 months and an additional leap year month in the Ahom sexagenary calendar known as Lak-ni. [4] [5] The first month is Duin Shing. [6]

No.NameAhom scriptGregorian Month
1Duin-Shing𑜓𑜢𑜤𑜃𑜫 𑜋𑜢𑜂𑜫 November-December
2Duin-Kam𑜓𑜢𑜤𑜃𑜫 𑜀𑜪 December-January
3Duin-Tsam𑜓𑜢𑜤𑜃𑜫 𑜏𑜪 January-February
4Duin-Shi𑜓𑜢𑜤𑜃𑜫 𑜏𑜢 February-March
5Duin-Ha𑜓𑜢𑜤𑜃𑜫 𑜑𑜡 March-April
6Duin-Rok𑜓𑜢𑜤𑜃𑜫 𑜍𑜤𑜀𑜫 April-May
7Duin-Shit𑜓𑜢𑜤𑜃𑜫 𑜋𑜢𑜄𑜫 May-June
8Duin-paet𑜓𑜢𑜤𑜃𑜫 𑜆𑜢𑜤𑜄𑜫 June-July
9Duin-kauo𑜓𑜢𑜤𑜃𑜫 𑜀𑜰𑜫 July-August
10Duin-sip𑜓𑜢𑜤𑜃𑜫 𑜏𑜢𑜆𑜫 August-September
11Duin-tsip-it𑜓𑜢𑜤𑜃𑜫 𑜏𑜢𑜆𑜫 𑜒𑜪𑜄𑜫 September-October
12Duin-sip-song𑜓𑜢𑜤𑜃𑜫 𑜏𑜢𑜆𑜫 𑜁 October-November

Roman calendar

The Roman calendar 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 Gregorian calendar, like the Roman calendars before it, has twelve months, whose Anglicized names are:

of days
1 January 31
2 February 28
29 in leap years
3 March 31
4 April 30
5 May 31
6 June 30
7 July
formerly Quinctilis
8 August
formerly Sextilis
9 September 30
10 October 31
11 November 30
12 December 31
On top of the knuckles (yellow): 31 days
Between the knuckles (blue): 30 days
February (red) has 28 or 29 days. Month - Knuckles (en).svg
On top of the knuckles (yellow): 31 days
Between the knuckles (blue): 30 days
February (red) has 28 or 29 days.
The white keys of the musical keyboard correspond to months with 31 day months. (F corresponds to January.) Klaviatur-3-en.svg
The white keys of the musical keyboard correspond to months with 31 day months. (F corresponds to January.)

The famous mnemonic 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. [7] [8]

This cyclical pattern of month lengths matches the musical keyboard 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 Roman calendar included:

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 are always the first day of the month, [lower-alpha 1] 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 Hebrew calendar has 12 or 13 months.

  1. Nisan, 30 days ניסן
  2. Iyar, 30 days אייר
  3. Sivan, 30 days סיון
  4. Tammuz, 29 days תמוז
  5. Av, 30 days אב
  6. Elul, 29 days אלול
  7. Tishri, 30 days תשרי
  8. Marcheshvan, 29/30 days מַרְחֶשְׁוָן
  9. Kislev, 30/29 days כסלו
  10. Tevet, 29 days טבת
  11. Shevat, 30 days שבט
  12. Adar 1, 30 days, intercalary month אדר א
  13. 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:

  1. Muharram (Restricted/sacred) محرّم
  2. Safar (Empty/Yellow) صفر
  3. Rabī' al-Awwal/Rabi' I (First Spring) ربيع الأول
  4. Rabī' ath-Thānī/Rabi' al-Aakhir/Rabi' II (Second spring or Last spring) ربيع الآخر أو ربيع الثاني
  5. Jumada al-Awwal/Jumaada I (First Freeze) جمادى الأول
  6. Jumada ath-Thānī or Jumādā al-Thānī/Jumādā II (Second Freeze or Last Freeze) جمادى الآخر أو جمادى الثاني
  7. Rajab (To Respect) رجب
  8. Sha'bān (To Spread and Distribute) شعبان
  9. Ramadān (Parched Thirst) رمضان
  10. Shawwāl (To Be Light and Vigorous) شوّال
  11. Dhu al-Qi'dah (The Master of Truce) ذو القعدة
  12. Dhu al-Hijjah (The Possessor of Hajj) ذو الحجة

See Islamic calendar for more information on the Islamic calendar.

Arabic calendar

Gregorian monthArabic month
January ينايركانون الثانيKanun Al-Thani
February فبرايرشباطShebat
March مارساذارAdhar
April ابريلنيسانNisan
May مايوأيّارAyyar
June يونيوحزيرانḨazayran
July يوليوتمّوزTammuz
August أغسطساَبʕAb
September سبتمبرأيلولAylul
October أكتوبرتشرين الأولTishrin Al-Awwal
November نوفمبرتشرين الثانيTishrin Al-Thani
December ديسمبركانون الأولKanun Al-Awwal

Hindu calendar

The Hindu calendar has various systems of naming the months. The months in the lunar calendar are:

Sanskrit nameTamil nameTelugu nameNepali nameAssamese name
1 Vaiśākha (वैशाख)Vaikasi (வைகாசி)Vaisaakhamu (వైశాఖము) Baisakh (बैशाख)Bahāg (বহাগ)
2 Jyeṣṭha (ज्येष्ठ)Aani (ஆனி)Jyeshttamu (జ్యేష్ఠము) Jeth (जेष्ठ/जेठ)Jeth (জেঠ)
3 Ashadha (आषाढ)Aadi (ஆடி)Aashaadhamu (ఆషాఢము) Asaar (आषाढ/असार)Āsār/Āhār (আষাঢ়/আহাৰ)
4 Śrāvaṇa (श्रावण) Aavani (ஆவணி)Sraavanamu (శ్రావణము) Saaoon (श्रावण/साउन)Sāoon (শাওণ)
5 Bhadrapada (भाद्रपद)Purratasi (புரட்டாசி)Bhaadhrapadamu (భాద్రపదము) Bhadau (भाद्र|भदौ)Bhādo (ভাদ)
6 Āśvina (अश्विन)Aiypasi (ஐப்பசி)Aasveeyujamu (ఆశ్వయుజము) Asoj (आश्विन/असोज)Āhin (আহিন)
7 Kārtika (कार्तिक/कात्तिक)Kaarthigai (கார்த்திகை)Kaarthikamu (కార్తీకము) Kaattick(कार्तिक/ कात्तिक)Kāti (কাতি)
8 Mārgaśīrṣa (मार्गशीर्ष) Maargazhi (மார்கழி)Maargaseershamu (మార్గశిరము) Mangsir (मार्ग/मंसिर)Āghun (আঘোণ)
9 Pauṣa (पौष)Thai (தை)Pushyamu (పుష్యము) Push (पौष/पुष/पूस)Puh (পুহ)
10 Māgha (माघ) Maasi (மாசி)Maaghamu (మాఘము) Magh (माघ)Māgh (মাঘ)
11 Phālguna (फाल्गुन) Panguni (பங்குனி)Phaalgunamu (ఫాల్గుణము) Faagoon (फाल्गुन/फागुन)Fāgoon (ফাগুণ)
12 Chaitra (चैत्र)Chitirai (சித்திரை)Chaithramu (చైత్రము) Chait (चैत्र/चैत)Chot (চ'ত)

These are also the names used in the Indian national calendar for the newly redefined months. Purushottam Maas or Adhik Maas (translit. adhika = 'extra', māsa = 'month') is an extra month in the Hindu calendar that is inserted to keep the lunar and solar calendars aligned. "Purushottam" is an epithet of Vishnu, to whom the month is dedicated.

The names in the solar calendar are just the names of the zodiac sign in which the sun travels. They are

  1. Mesha
  2. Vrishabha
  3. Mithuna
  4. Kataka
  5. Simha
  6. Kanyaa
  7. Tulaa
  8. Vrishcika
  9. Dhanus
  10. Makara
  11. Kumbha
  12. Miina

Baháʼí calendar

The Baháʼí calendar is the calendar used by the Baháʼí Faith. It is a solar calendar with regular years of 365 days, and leap years of 366 days. Years are composed of 19 months of 19 days each (361 days), plus an extra period of "Intercalary Days" (4 in regular and 5 in leap years). [9] The months are named after the attributes of God. Days of the year begin and end at sundown. [9]

Iranian calendar (Persian calendar)

The Iranian / Persian calendar, currently used in Iran, also has 12 months. The Persian names are included in the parentheses. It begins on the northern Spring equinox.

  1. Farvardin (31 days, فروردین)
  2. Ordibehesht (31 days, اردیبهشت)
  3. Khordad (31 days, خرداد)
  4. Tir (31 days, تیر)
  5. Mordad (31 days, مرداد)
  6. Shahrivar (31 days, شهریور)
  7. Mehr (30 days, مهر)
  8. Aban (30 days, آبان)
  9. Azar (30 days, آذر)
  10. Dey (30 days, دی)
  11. Bahman (30 days, بهمن)
  12. Esfand (29 days- 30 days in leap year, اسفند)

Reformed Bengali calendar

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

No.Name (Bengali)Name (Sylheti)Name (Rohingya)SeasonDaysRoman months
1 Boishakh (বৈশাখ) Boishakh Boicák Grishmo (গ্রীষ্ম) 3114 April – May
2 Joishtho (জ্যৈষ্ঠ) Zoit Zeth Grishmo (গ্রীষ্ম) 31May – June
3 Asharh (আষাঢ়) Aaŗ Acár Borsha (বর্ষা) 31June – July
4 Shrabon (শ্রাবণ) Haon Cón Borsha (বর্ষা) 31July – August
5 Bhadro (ভাদ্র) Bhado Bádo Shorot (শরৎ) 31August – September
6 Aashin (আশ্বিন) Ashin Acín Shorot (শরৎ) 30September – October
7 Kartik (কার্তিক) Khati Hati Hemonto(হেমন্ত) 30October – November
8 Ogrohayon (অগ্রহায়ণ) Aghon Óon Hemonto(হেমন্ত) 30November – December
9 Poush (পৌষ) Phush Fuc Sheet (শীত) 30December – January
10 Magh (মাঘ) Magh (মাঘ) Mak Sheet (শীত) 30January – February
11 Falgun (ফাল্গুন) Fagun Fóon Boshonto (বসন্ত) 30 (31 in leap years)February – March
12 Choitro (চৈত্র) Soit Soit Boshonto (বসন্ত) 30March – April

Nanakshahi calendar

The months in the Nanakshahi calendar are: [10]

No.Name Punjabi DaysJulian months
1 Chet ਚੇਤ3114 March – 13 April
2 Vaisakh ਵੈਸਾਖ3114 April – 14 May
3 Jeth ਜੇਠ3115 May – 14 June
4 Harh ਹਾੜ3115 June – 15 July
5 Sawan ਸਾਵਣ3116 July – 15 August
6 Bhadon ਭਾਦੋਂ3016 August – 14 September
7 Assu ਅੱਸੂ3015 September – 14 October
8 Katak ਕੱਤਕ3015 October – 13 November
9 Maghar ਮੱਘਰ3014 November – 13 December
10 Poh ਪੋਹ3014 December – 12 January
11 Magh ਮਾਘ3013 January – 11 February
12 Phagun ਫੱਗਣ30/3112 February – 13 March

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.

Gregorian monthMeaningZodiac sign
JanuaryមករាMôkâréaMakarāមករ (UNGEGN: môkâr, ALA-LC: makar); "naga" Capricorn
Februaryកុម្ភៈKŏmpheăKumbhàក្អម (UNGEGN: k'âm, ALA-LC: kʿʹam); "clay pitcher" Aquarius
Marchមិនា/មីនាMĭnéa/MinéaMinā/Mīnāត្រី (UNGEGN: trei, ALA-LC: trī); "fish" or "three/third" Pisces
AprilមេសាMésaMesāចៀម (UNGEGN: chiĕm, ALA-LC: ciam); "sheep" Aries
MayឧសភាŬsâphéaUsabhāគោឈ្មោល (UNGEGN: koŭ chhmoŭl, ALA-LC: go jhmol); "bull" Taurus
JuneមិថុនាMĭthŏnéaMithunāគូ (UNGEGN: ku, ALA-LC: ); "couple" Gemini
Julyកក្កដាKâkkâdakakkaṭāក្ដាម (UNGEGN: kdam, ALA-LC: kṭām); "crab" Cancer
AugustសីហាSeihaSīhāសីហៈ (UNGEGN: seihă, ALA-LC: sīhà); "lion" Leo
Septemberកញ្ញាKânhnhéaKaññāក្រមុំ (UNGEGN: krâmŭm, ALA-LC: kramuṃ); "maiden" Virgo
OctoberតុលាTŏléaTulāជញ្ជីង (UNGEGN: chônhching, ALA-LC: jañjīng); "scales" Libra
Novemberវិច្ឆិកាVĭchchhĕkaVicchikāខ្ទួយ (UNGEGN: khtuŏy, ALA-LC: khtuay); "scorpion" Scorpio
Decemberធ្នូThnuDhnūធ្នូ (UNGEGN: thnu, ALA-LC: dhnū); "bow", "arc" Sagittarius

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. [11] 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.

No.Khmer month
(8a, 8b)
(បឋមសាឍ, ទុតិយាសាឍ)
(Bâthâmôsath, Tŭtĕyéasath)
ʿʹāsāḍh (Paṭhamasāḍh, Dutiyāsāḍh)
9ស្រាពណ៍SrapônSrābaṇ ̊

Thai calendar

English nameThai nameAbbr.TranscriptionSanskrit wordZodiac sign
Januaryมกราคมม.ค.mokarakhommakara "sea-monster" Capricorn
Februaryกุมภาพันธ์ก.พ.kumphaphankumbha "pitcher, water-pot" Aquarius
Marchมีนาคมมี.ค.minakhommīna "(a specific kind of) fish" Pisces
Aprilเมษายนเม.ย.mesayonmeṣa "ram" Aries
Mayพฤษภาคมพ.ค.phruetsaphakhomvṛṣabha "bull" Taurus
Juneมิถุนายนมิ.ย.mithunayonmithuna "a pair" Gemini
Julyกรกฎาคมก.ค.karakadakhomkarkaṭa "crab" Cancer
Augustสิงหาคมส.ค.singhakhomsiṃha "lion" Leo
Septemberกันยายนก.ย.kanyayonkanyā "girl" Virgo
Octoberตุลาคมต.ค.tulakhomtulā "balance" Libra
Novemberพฤศจิกายนพ.ย.phruetsachikayonvṛścika "scorpion" Scorpio
Decemberธันวาคมธ.ค.thanwakhomdhanu "bow, arc" Sagittarius

Tongan calendar

The Tongan calendar is based on the cycles of the Moon around the Earth in one year. The months are:

  1. Liha Mu'a
  2. Liha Mui
  3. Vai Mu'a
  4. Vai Mui
  5. Faka'afu Mo'ui
  6. Faka'afu Mate
  7. Hilinga Kelekele
  8. Hilinga Mea'a
  9. 'Ao'ao
  10. Fu'ufu'unekinanga
  11. 'Uluenga
  12. Tanumanga
  13. 'O'oamofanongo


Pingelapese, a language from Micronesia, also uses a lunar calendar. There are 12 months associated with their calendar. The Moon first appears in March,[ clarification needed ] 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. [12]

Kollam era (Malayalam) calendar

Malayalam nameTransliterationConcurrent Gregorian monthsSanskrit word and meaningZodiac sign
ചിങ്ങംchi-ngnga-mAugust–Septembersimha "lion" Leo
കന്നിka-nniSeptember–Octoberkanyā "girl" Virgo
തുലാംthu-lā-mOctober–Novembertulā "balance" Libra
വൃശ്ചികംvRSh-chi-ka-mNovember–Decembervṛścika "scorpion" Scorpio
ധനുdha-nuDecember–Januarydhanu "bow, arc" Sagittarius
മകരംma-ka-ra-mJanuary–Februarymokara "sea-monster" Capricorn
കുംഭംkum-bha-mFebruary–Marchkumbha "pitcher, water-pot" Aquarius
മീനംmee-na-mMarch–Aprilmīna "(a specific kind of) fish" Pisces
മേടംmE-Da-mApril–Maymeṣa "ram" Aries
ഇടവംi-Ta-va-mMay – Junevṛṣabha "bull" Taurus
മിഥുനംmi-thu-na-mJune–Julymithuna "a pair" Gemini
കർക്കടകംkar-kka-Ta-ka-mJuly–Augustkarkaṭa "crab" Cancer

Sinhalese calendar

The Sinhalese calendar is the Buddhist calendar in Sri Lanka with Sinhala names. Each full moon Poya day marks the start of a Buddhist lunar month. [13] The first month is Bak. [14] [15]

  1. Duruthu (දුරුතු)
  2. Navam (නවම්)
  3. Mædin (මැදින්)
  4. Bak (බක්)
  5. Vesak (වෙසක්)
  6. Poson (පොසොන්)
  7. Æsala (ඇසල)
  8. Nikini (නිකිණි)
  9. Binara (බිනර)
  10. Vap (වප්)
  11. Il (iL) (ඉල්)
  12. 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 rather than on the same date. Hence Þorri always starts on a Friday sometime between January 22 and January 28 (Old style: January 9 to January 15), Góa always starts on a Sunday between February 21 and February 27 (Old style: February 8 to February 14).

  1. Gormánuður (mid-October – mid-November, "slaughter month" or "Gór's month")
  2. Ýlir (mid-November – mid-December, "Yule month")
  3. Mörsugur (mid-December – mid-January, "fat sucking month")
  4. Þorri (mid-January – mid-February, "frozen snow month")
  5. Góa (mid-February – mid-March, "Góa's month, see Nór")
  6. Einmánuður (mid-March – mid-April, "lone" or "single month")
  1. 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)
  2. Skerpla (mid-May – mid-June, another forgotten goddess)
  3. Sólmánuður (mid-June – mid-July, "sun month")
  4. Heyannir (mid-July – mid-August, "hay business month")
  5. Tvímánuður (mid-August – mid-September, "two" or "second month")
  6. Haustmánuður (mid-September – mid-October, "autumn month")

Old Georgian calendar

MonthGeorgian month nameTransliterationGeorgian other namesTransliteration
January აპნისი, აპანიApnisi, Apani  
February სურწყუნისიSurtskunisiგანცხადებისთვეGantskhadebistve
March მირკანიMirkani  
April იგრიკაIgrika  
May ვარდობისაVardobisaვარდობისთვეVardobistve
June მარიალისაMarialisaთიბათვე, ივანობისთვეTibatve, Ivanobistve
July თიბისაTibisaმკათათვე, კვირიკობისთვეMkatatve, Kvirikobistve
August ქველთობისაKveltobisaმარიამობისთვეMariamobistve
September ახალწლისაAkhaltslisaენკენისთვეEnkenistve
October სთვლისაStvlisaღვინობისთვეGvinobistve
November ტირისკონიTiriskoniგიორგობისთვე, ჭინკობისთვეGiorgobistve, Chinkobistve
December ტირისდენიTirisdeniქრისტეშობისთვეKristeshobistve

*NOTE:New Year in ancient Georgia started from September.

Old Swedish calendar

  1. Torsmånad (January, 'Torre's month' (ancient god))
  2. Göjemånad (February, 'Goe's month' (ancient goddess))
  3. Vårmånad (March, 'Spring month')
  4. Gräsmånad (April, 'Grass month')
  5. Blomstermånad (May, 'Bloom month')
  6. Sommarmånad (June, 'Summer month')
  7. Hömånad (July, 'Hay month')
  8. Skördemånad, Rötmånad (August, 'Harvest month' or 'Rot month')
  9. Höstmånad (September, 'Autumn month')
  10. Slaktmånad (October, 'Slaughter month')
  11. Vintermånad (November, 'Winter month')
  12. Julmånad (December, 'Christmas month')

Old English calendar

Like the Old Norse calendar, the Anglo-Saxons had their own calendar before they were Christianized which reflected native traditions and deities. These months were attested by Bede in his works On Chronology and The Reckoning of Time written in the 8th century. [16] His Old English month names are probably written as pronounced in Bede's native Northumbrian dialect. 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.

Old English month names
from Bede's The Reckoning of Time
Old English
Modern English
1 Æfterra-ġēola mōnaþ   “After-Yule month”January
2 Sol-mōnaþ “Sol month”February
3 Hrēð-mōnaþ Hreth month”March
4 Ēostur-mōnaþ Ēostur month”
5 Ðrimilce-mōnaþ “Three-milkings month”   
6 Ærra-Liþa “Ere-Litha
7 Æftera-Liþa “After-Litha
8 Weōd-mōnaþ “Weed month”
9 Hāliġ-mōnaþ or
“Holy month” or
“Harvest month”
10 Winter-fylleþ “Winter-filleth”
11 Blōt-mōnaþ Blót month”
12 Ærra-ġēola mōnaþ “Ere-Yule

When an intercalary month was needed, a third Litha month was inserted in mid-summer. [16]

Old Celtic calendar

The Coligny calendar (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.

NameDaysMeaningModern months
I-1Unknown30Intercalary One
1Samonios30summer monthMay-June
3Rivros30fat monthJuly-August
5Ogronios30cold monthSeptember-October
6Cutios30wind monthOctober-November
I-2[.]antaran[...]30Intercalary Two
7Giamonios29winter monthNovember-December
9Equos29 or 30January-February
11Edrinios30month of heatMarch-April
12Cantlos29month of songApril-May

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 [17] but eventually came to correspond to the Gregorian months as shown below: [18]

  1. Boldogasszony hava (January, 'month of the happy/blessed lady')
  2. Böjtelő hava (February, 'month of early fasting/Lent' or 'month before fasting/Lent')
  3. Böjtmás hava (March, 'second month of fasting/Lent')
  4. Szent György hava (April, 'Saint George's month')
  5. Pünkösd hava (May, 'Pentecost month')
  6. Szent Iván hava (June, 'Saint John [the Baptist]'s month')
  7. Szent Jakab hava (July, 'Saint James' month')
  8. Kisasszony hava (August, 'month of the Virgin')
  9. Szent Mihály hava (September, 'Saint Michael's month')
  10. Mindszent hava (October, 'all saints' month')
  11. Szent András hava (November, 'Saint Andrew's month')
  12. Karácsony hava (December, 'month of Yule/Christmas')

Czech calendar

  1. Leden – derives from 'led' (ice)
  2. Únor – derives from 'nořit' (to dive, referring to the ice sinking into the water due to melting)
  3. Březen – derives from 'bříza' (birch)
  4. Duben – derives from 'dub' (oak)
  5. Květen – derives from 'květ' (flower)
  6. Červen – derives from 'červená' (red – for the color of apples and tomatoes)
  7. Červenec – is the second 'červen' (formerly known as 2nd červen)
  8. Srpen – derives from old Czech word 'sirpsti' (meaning to reflect, referring to the shine on the wheat)
  9. Září – means 'to shine'
  10. Říjen – derives from 'jelení říje', which refers to the estrous cycle of female elk
  11. Listopad – falling leaves
  12. Prosinec – derives from old Czech 'prosiněti', which means to shine through (refers to the sun light shining through the clouds) [19]

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. [20] 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".

  1. Thout
  2. Paopi
  3. Hathor
  4. Koiak
  5. Tooba
  6. Emshir
  7. Paremhat
  8. Paremoude
  9. Pashons
  10. Paoni
  11. Epip
  12. Mesori

Nisga'a calendar

The Nisga'a calendar coincides with the Gregorian calendar with each month referring to the type of harvesting that is done during the month.[ citation needed ]

  1. K'aliiyee = Going North – referring to the Sun returning to its usual place in the sky
  2. Buxwlaks = Needles Blowing About – February is usually a very windy month in the Nass River Valley
  3. Xsaak = To Eat Oolichans – Oolichans are harvested during this month
  4. Mmaal = Canoes – The river has defrosted, hence canoes are used once more
  5. Yansa'alt = Leaves are Blooming – Warm weather has arrived and leaves on the trees begin to bloom
  6. Miso'o = Sockeye – majority of Sockeye Salmon runs begin this month
  7. Maa'y = Berries – berry picking season
  8. Wii Hoon = Great Salmon – referring to the abundance of Salmon that are now running
  9. Genuugwwikw = Trail of the Marmot – Marmots, Ermines and animals as such are hunted
  10. Xlaaxw = To Eat Trout – trout are mostly eaten this time of year
  11. Gwilatkw = To Blanket – The earth is "blanketed" with snow
  12. 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:

  1. Vendémiaire
  2. Brumaire
  3. Frimaire
  1. Nivôse
  2. Pluviôse
  3. Ventôse
  1. Germinal
  2. Floréal
  3. Prairial
  1. Messidor
  2. Thermidor
  3. Fructidor

Eastern Ojibwe calendar

Ojibwe month names [lower-alpha 2] 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 [21] also informs of not only the variability in the month names, but how in Eastern Ojibwe these names were originally applied to the lunar months the Ojibwe originally used, which was a lunisolar calendar, fixed by the date of Akiinaaniwan (typically December 27) that marks when sunrise is the latest in the Northern Hemisphere.

Month in
Eastern Ojibwe [lower-alpha 2]
Original order in the Ojibwa yearStarting at the first full moon after:
in those places that have a sucker run during that time
n[a]mebin-giizis sucker moon
Akiinaaniwan on 27 December
February[o]naab[a]ni-giizisCrust-on-the-snow moon
25 January
Marchzii[n]z[i]baak[wa]doke-giizisSugaring moon
26 February
in those places that have a sucker run during that time
n[a]mebin-giizis sucker moon
25 March
in those places that do not have a sucker run during that time
waawaas[a]gone-giizisFlower moon
in those places that have an April sucker run
in those places that have a January sucker run
g[i]tige-giizisPlanting moon
24 April
in those places that have an April sucker run
in those places that have a January sucker run
[o]deh[i]min-giizisStrawberry moon
23 May
Julymiin-giizisBlueberry moon
22 June
August[o]dat[a]gaag[o]min-giizisBlackberry moon
20 July
Septemberm[an]daamin-giizisCorn moon
18 August
Octoberb[i]naakwe-giizisLeaves-fall moon
17 September
b[i]naakwii-giizisHarvest moon
Novemberg[a]shkadin-giizisFreeze-up moon
16 October
Decemberg[i]chi-b[i]boon-giizisBig-winter moon
15 November
in those places that do not have a sucker run during that time
[o]shki-b[i]boon-gii[zi]soonsLittle new-winter moon
(leap month)
only used if the new moon after g[i]chi-b[i]boon-giizis occurs before Akiinaaniwan on 27 December.

See also


  1. More precisely, the calends were when the name of a month first began being used when referring to dates. Instead of counting the number of days elapsed, the Romans used a countdown to number their dates. See the article Roman calendar for a more detailed explanation.
  2. 1 2 Due to Eastern Ojibwe is a vowel syncope dialect, the elided vowels (and the occasionally elided consonants) have been added back in the table below, shown in brackets.

Related Research Articles

<span class="mw-page-title-main">Calendar</span> System for organizing the days of year

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 physical record of such a system. A calendar can also mean a list of planned events, such as a court calendar, or a partly or fully chronological list of documents, such as a calendar of wills.

<span class="mw-page-title-main">Chinese calendar</span> Lunisolar calendar from China

The traditional Chinese calendar is a lunisolar calendar, combining the solar, lunar, and other cycles for various social and religious purposes. More recently, in China and Chinese communities the Gregorian calendar has been adopted and adapted in various ways, and is generally the basis for standard civic purposes, but incorporating traditional lunisolar holidays. However, there are many types and subtypes of the Chinese calendar, partly reflecting developments in astronomical observation and horology, with over a millennium plus history. The major modern form is the Gregorian calendar-based official version of the Mainland China, although diaspora versions are also notable in other parts of China and Chinese-influenced cultures; however, aspects of the traditional lunisolar calendar remain popular, including the association of the twelve animals of the Chinese Zodiac in relation to months and years.

<span class="mw-page-title-main">Full moon</span> Lunar phase: completely illuminated disc

The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon. This means that the lunar hemisphere facing Earth—the near side—is completely sunlit and appears as an approximately circular disk. The full moon occurs roughly once a month.

<span class="mw-page-title-main">Hebrew calendar</span> Lunisolar calendar used for Jewish religious observances

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 yahrzeits and the schedule of public Torah readings. In Israel, it is used for religious purposes, provides a time frame for agriculture, and is an official calendar for civil holidays alongside the Gregorian calendar.

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.

A leap year is a calendar year that contains an additional day compared to a common year. The 366th day is added to keep the calendar year synchronised with the astronomical year or seasonal year. Since astronomical events and seasons do not repeat in a whole number of days, calendars having a constant number of days each year will unavoidably drift over time with respect to the event that the year is supposed to track, such as seasons. By inserting ("intercalating") an additional day—a leap day—or month—a leap month—into some years, the drift between a civilization's dating system and the physical properties of the Solar System can be corrected.

A lunar calendar is a calendar based on the monthly cycles of the Moon's phases, in contrast to solar calendars, whose annual cycles are based on the solar year. The most widely observed purely lunar calendar is the Islamic calendar. A purely lunar calendar is distinguished from a lunisolar calendar, whose lunar months are brought into alignment with the solar year through some process of intercalation – such as by insertion of a leap month. The details of when months begin vary from calendar to calendar, with some using new, full, or crescent moons and others employing detailed calculations.

<span class="mw-page-title-main">Lunisolar calendar</span> Calendar with lunar month, solar year

A lunisolar calendar is a calendar in many cultures, incorporating lunar calendars and solar calendars. The date of lunisolar calendars therefore indicates both the Moon phase and the time of the solar year, that is the position of the Sun in the Earth's sky. If the sidereal year is used instead of the solar year, then the calendar will predict the constellation near which the full moon may occur. As with all calendars which divide the year into months there is an additional requirement that the year have a whole number of months. In some case ordinary years consist of twelve months but every second or third year is an embolismic year, which adds a thirteenth intercalary, embolismic, or leap month.

<span class="mw-page-title-main">Lunar phase</span> Shape of the Moons sunlit portion as viewed from Earth

A lunar phase or Moon phase is the apparent shape of the Moon's directly sunlit portion as viewed from the Earth. In common usage, the four major phases are the new moon, the first quarter, the full moon and the last quarter; the four minor phases are waxing crescent, waxing gibbous, waning gibbous, and waning crescent. A lunar month is the time between successive recurrences of the same phase: due to the eccentricity of the Moon's orbit, this duration is not perfectly constant but averages about 29.5 days.

<span class="mw-page-title-main">Metonic cycle</span> 19-year pattern in lunisolar calendars

The Metonic cycle or enneadecaeteris 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 observation the Metonic cycle defined as 235 synodic months is just 2 hours, 4 minutes and 58 seconds longer than 19 tropical years. Meton of Athens, in the 5th century BC, judged the cycle to be a whole number of days, 6,940. Using these whole numbers facilitates the construction of a lunisolar calendar.

<span class="mw-page-title-main">Year</span> Time of one planets orbit around a star

A year is the time taken for astronomical objects to complete one orbit. For example, a year on Earth is the time taken for Earth to revolve around the Sun. Generally, a year is taken to mean a calendar year, but the word is also used for periods loosely associated with the calendar or astronomical year, such as the seasonal year, the fiscal year, the academic year, etc. The term can also be used in reference to any long period or cycle, such as the Great Year.

A solar calendar is a calendar whose dates indicate 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. The main other types of calendar are lunar calendar and lunisolar calendar, whose months correspond to cycles of Moon phases. The months of the Gregorian calendar do not correspond to cycles of the Moon phase.

<span class="mw-page-title-main">Lunar day</span> Time for Moon to complete one rotation on its axis

A lunar day is the time it takes for Earth's Moon to complete on its axis one synodic rotation, meaning with respect to the Sun. The lunar day is therefore the time of a full lunar day-night cycle. Due to tidal locking, this equals the time that the Moon takes to complete one synodic orbit around Earth, a synodic lunar month, returning to the same lunar phase. The synodic period is about 29+12 Earth days, which is about 2.2 days longer than its sidereal period.

The Hindu calendar, also called 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. They adopt a similar underlying concept for timekeeping based on sidereal year for solar cycle and adjustment of lunar cycles in every three years, but differ in their relative emphasis to moon cycle or the sun cycle and the names of months and when they consider the New Year to start. Of the various regional calendars, the most studied and known Hindu calendars are the Shalivahana Shaka found in the Deccan region of Southern India and the Vikram Samvat (Bikrami) found in Nepal and the North and Central regions of India – both of which emphasize the lunar cycle. Their new year starts in spring. In regions such as Tamil Nadu and Kerala, the solar cycle is emphasized and this is called the Tamil calendar and Malayalam calendar and these have origins in the second half of the 1st millennium CE. A Hindu calendar is sometimes referred to as Panchangam (पञ्चाङ्गम्), which is also known as Panjika in Eastern India.

Calendar reform or calendrical reform is any significant revision of a calendar system. The term sometimes is used instead for a proposal to switch to a different calendar design.

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 official occasions. While the calendars share a common lineage, they also have minor but important variations such as intercalation schedules, month names and numbering, use of cycles, etc. In Thailand, the name Buddhist Era is a year numbering system shared by the traditional Thai lunar calendar and by the Thai solar calendar.

Vikram Samvat, also known as the Vikrami calendar is a Hindu calendar historically used in the Indian subcontinent and still used in several states. It is a solar calendar, using twelve to thirteen lunar months each solar sidereal years. The year count of the Vikram Samvat calendar is usually 57 years ahead of the Gregorian calendar, except during January to April, when it is ahead by 56 years.

The Burmese calendar is a lunisolar calendar in which the months are based on lunar months and years are based on sidereal years. The calendar is largely based on an older version of the Hindu calendar, though unlike the Indian systems, it employs a version of the Metonic cycle. The calendar therefore has to reconcile the sidereal years of the Hindu calendar with the Metonic cycle's near tropical years by adding intercalary months and days at irregular intervals.

Nisan-years is an ancient calendar system used around Mesopotamia. Its beginning was from the prehistorical era. Ever since Mesopotamia had historical writings, even before the First Babylonian dynasty of Hammurabi, its calendar used the Nisan-years.

<span class="mw-page-title-main">Lunar month</span> Time between successive new moons

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.


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