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.
Ahom calendar The
Ahom people live in
Assam, eastern
India. Their
sexagenary calendar known as Lak-ni has 12 months and an additional leap year month. The first month is Duin Shing.
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: : 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. 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: •
Intercalaris an
intercalary month occasionally embedded into February, to realign the calendar. •
Quintilis, later renamed to
Julius in honour of
Julius Caesar. •
Sextilis, later renamed to
Augustus in honour of
Augustus. 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, 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 Variants of the traditional hebrew calendar are known from the 1st millenium BCE. Around 350CE it adopted the
metonic cycle. Today it is used for religious needs only, while daily life is conducted according to the Gregorian calendar. In the 1st millenium BCE, the year began in the month of Nissan. From the 2nd century BCE, the year begins in Tishrei. Today the first day of Tishrei is the first day of the new year. The
Hebrew calendar has 12 or 13 months. •
Nisan, 30 days ניסן •
Iyar, 30 days אייר •
Sivan, 30 days סיון •
Tammuz, 29 days תמוז •
Av, 30 days אב •
Elul, 29 days אלול •
Tishrei, 30 days תשרי •
Marheshvan (Heshvan), 29/30 days (חשון) מַרְחֶשְׁוָן •
Kislev, 30/29 days כסלו •
Tevet, 29 days טבת •
Shevat, 30 days שבט •
Adar 1, 30 days,
intercalary month אדר א •
Adar 2, 29 days אדר ב In leap years, an extra month is added, being Adar 1. It is added 7 times in every 19 years long cycle. 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 (Restricted/sacred) محرّم •
Safar (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-Aakhir/Jumādā II (Second Freeze or Last Freeze) جمادى الآخر أو جمادى الثاني •
Rajab (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 (The Master of Truce) ذو القعدة •
Dhu al-Hijjah (The Possessor of Hajj) ذو الحجة See
Islamic calendar for more information on the Islamic calendar.
Arabic calendar Hindu calendar The
Hindu calendar 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 for the newly redefined months. Purushottam Maas or Adhik Maas (
translit. '''' = 'extra', '''' = '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 •
Mesha •
Vrishabha •
Mithuna •
Kataka •
Simha •
Kanyaa •
Tulaa •
Vrishcika •
Dhanus •
Makara •
Kumbha •
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). 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, also has 12 months. The
Persian names are included in the parentheses. It begins on the northern Spring equinox. •
Farvardin (31 days, فروردین) •
Ordibehesht (31 days, اردیبهشت) •
Khordad (31 days, خرداد) •
Tir (31 days, تیر) •
Mordad (31 days, مرداد) •
Shahrivar (31 days, شهریور) •
Mehr (30 days, مهر) •
Aban (30 days, آبان) •
Azar (30 days, آذر) •
Dey (30 days, دی) •
Bahman (30 days, بهمن) •
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:
Nanakshahi calendar The months in the
Nanakshahi calendar 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. === Kollam era (
Malayalam) calendar ===
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. 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 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). • Skammdegi ("Short days") • Gormánuður (mid-October – mid-November, "slaughter month" or "
Gór's month") • Ýlir (mid-November – mid-December, "
Yule 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") • 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 month") • Heyannir (mid-July – mid-August, "
hay 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 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 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. 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. : When an
intercalary month was needed, a third
Litha month was inserted in mid-summer.
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.
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 [the Baptist]'s month') • Szent Jakab hava (July, 'Saint James' month') • Kisasszony hava (August, 'month of the
Virgin') • 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 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 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 •
Brumaire •
Frimaire • Winter: •
Nivôse •
Pluviôse •
Ventôse • Spring: •
Germinal •
Floréal •
Prairial • Summer: •
Messidor •
Thermidor •
Fructidor Eastern Ojibwe calendar Ojibwe 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
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. : == See also ==