astronomy Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, g ...

, the new moon is the first

lunar phase Concerning the lunar month of ~29.53 days as viewed from Earth, the lunar phase or Moon phase is the shape of the Moon's directly sunlit portion, which can be expressed quantitatively using areas or angles, or described qualitatively using the t ...

, when the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

and

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

have the same

ecliptic longitude The ecliptic coordinate system is a celestial coordinate system commonly used for representing the apparent positions, orbits, and pole orientations of Solar System objects. Because most planets (except Mercury) and many small Solar System b ...

. At this phase, the lunar disk is not visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection. Vision corrected to norma ...

, except when it is silhouetted against the Sun during a

solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an eclipse season, approximately every six mon ...

. The original meaning of the term 'new moon', which is still sometimes used in calendrical, non-astronomical contexts, is the first visible

crescent A crescent shape (, ) is a symbol or emblem used to represent the lunar phase in the first quarter (the "sickle moon"), or by extension a symbol representing the Moon itself. In Hinduism, Lord Shiva is often shown wearing a crescent moon on his ...

of the Moon after

conjunction Conjunction may refer to: * Conjunction (grammar), a part of speech * Logical conjunction, a mathematical operator ** Conjunction introduction, a rule of inference of propositional logic * Conjunction (astronomy), in which two astronomical bodies ...

with the Sun. This thin

waxing Waxing is the process of hair removal from the root by using a covering of a sticky substance, such as wax, to adhere to body hair, and then removing this covering and pulling out the hair from the follicle. New hair will not grow back in the pr ...

crescent is briefly and faintly visible as the Moon gets lower in the western sky after

sunset Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth (except the North and South poles), the equinox Sun sets due west at the moment of both the spr ...

. The precise time and even the date of the appearance of the new moon by this definition will be influenced by the geographical location of the observer. The first crescent marks the beginning of the month in the

Islamic calendar The Hijri calendar ( ar, ٱلتَّقْوِيم ٱلْهِجْرِيّ, translit=al-taqwīm al-hijrī), also known in English as the Muslim calendar and Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 ...

and in some

lunisolar calendar A lunisolar calendar is a calendar in many cultures, combining 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 ...

s such as the

Hebrew calendar The Hebrew calendar ( he, הַלּוּחַ הָעִבְרִי, translit=HaLuah HaIvri), also called the Jewish calendar, is a lunisolar calendar used today for Jewish religious observance, and as an official calendar of the state of Israel ...

. In the

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

, the beginning of the month is marked by the last visible crescent of a

waning Concerning the lunar month of ~29.53 days as viewed from Earth, the lunar phase or Moon phase is the shape of the Moon's directly sunlit portion, which can be expressed quantitatively using areas or angles, or described qualitatively using the t ...

Moon. The astronomical new moon occurs by definition at the moment of conjunction in ecliptical longitude with the Sun when the Moon is invisible from the Earth. This moment is unique and does not depend on location, and in certain circumstances, it coincides with a

. A

lunation 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 ...

, or

synodic 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 ...

, is the time period from one new moon to the next. At the J2000.0 epoch, the average length of a lunation is 29.53059

day A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours, 1440 minutes, or 86,400 seconds. In everyday life, the word "day" often refers to a solar day, which is the length between two ...

s (or 29 days, 12 hours, 44 minutes, and 3 seconds). However, the length of any one synodic month can vary from 29.26 to 29.80 days (12.96 hours) due to the perturbing effects of the Sun's gravity on the Moon's

eccentric orbit In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values betwee ...

Lunation number

The ''Lunation Number'' or ''Lunation Cycle'' is a number given to each

beginning from a certain one in history. Several conventions are in use. The most commonly used was the

Brown Brown is a color. It can be considered a composite color, but it is mainly a darker shade of orange. In the CMYK color model used in printing or painting, brown is usually made by combining the colors orange and black. In the RGB color model ...

Lunation Number (BLN), which defines lunation 1 as beginning at the first new moon of 1923, the year when Ernest William Brown's

lunar theory Lunar theory attempts to account for the motions of the Moon. There are many small variations (or perturbations) in the Moon's motion, and many attempts have been made to account for them. After centuries of being problematic, lunar motion can now ...

was introduced in the

American Ephemeris and Nautical Almanac ''The American Ephemeris and Nautical Almanac'' was published for the years 1855 to 1980, containing information necessary for astronomers, surveyors, and navigators. It was based on the original British publication, '' The Nautical Almanac and Ast ...

. Lunation 1 occurred at approximately 02:41 UTC, January 17, 1923. With later refinements, the BLN was used in almanacs until 1983. A more recent lunation number (simply called the Lunation Number) was introduced by

Jean Meeus Jean Meeus (born 12 December 1928) is a Belgian meteorologist and amateur astronomer specializing in celestial mechanics, spherical astronomy, and mathematical astronomy. Meeus studied mathematics at the University of Leuven in Belgium, w ...

in 1998. defines lunation 0 as beginning on the first new moon of 2000 (this occurred at approximately 18:14 UTC, January 6, 2000). The formula relating Meeus's Lunation Number with the Brown Lunation Number is: BLN = LN + 953. The Goldstine Lunation Number refers to the lunation numbering used by

Herman Goldstine Herman Heine Goldstine (September 13, 1913 – June 16, 2004) was a mathematician and computer scientist, who worked as the director of the IAS machine at Princeton University's Institute for Advanced Study and helped to develop ENIAC, th ...

, with lunation 0 beginning on January 11, 1001 BCE, and can be calculated using GLN = LN + 37105. The Hebrew Lunation Number is the count of lunations in the

with lunation 1 beginning on October 6, 3761 BCE. It can be calculated using HLN = LN + 71234. The Islamic Lunation Number is the count of lunations in the

Islamic Calendar The Hijri calendar ( ar, ٱلتَّقْوِيم ٱلْهِجْرِيّ, translit=al-taqwīm al-hijrī), also known in English as the Muslim calendar and Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 ...

with lunation 1 as beginning on the first day of the month of

Muharram Muḥarram ( ar, ٱلْمُحَرَّم) (fully known as Muharram ul Haram) is the first month of the Islamic calendar. It is one of the four sacred months of the year when warfare is forbidden. It is held to be the second holiest month after ...

, which occurred in 622 CE (July 15, Julian, in the proleptic reckoning). It can be calculated using ILN = LN + 17038. The Thai Lunation Number is called "มาสเกณฑ์" (Maasa-Kendha), defines lunation 0 as the beginning of Burmese era of the

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

on Sunday, March 22, 638 CE. It can be calculated using TLN = LN + 16843.

Lunisolar calendars

Hebrew calendar

The new moon, in Hebrew

Rosh Chodesh Rosh Chodesh or Rosh Hodesh ( he, ראש חודש; trans. ''Beginning of the Month''; lit. ''Head of the Month'') is the name for the first day of every month in the Hebrew calendar, marked by the birth of a new moon. It is considered a minor ...

, signifies the start of every Hebrew month and is considered an important date and minor holiday in the

. The modern form of the calendar practiced in Judaism is a rule-based

, akin to the

, measuring months defined in lunar cycles as well as years measured in solar cycles, and distinct from the purely lunar

and the predominantly solar

Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years d ...

. The Jewish months are fixed to the annual seasons by setting the new moon of

Aviv Aviv ( he, אביב) means "barley ripening", and by extension "spring season" in Hebrew. It is also used as a given name, surname, and place name, as in Tel Aviv. The first month of the year is called the month of Aviv in the Pentateuch. The mo ...

, the ''barley ripening'', or ''spring'', as the first moon and head of the year. Since the

Babylonian captivity The Babylonian captivity or Babylonian exile is the period in Jewish history during which a large number of Judeans from the ancient Kingdom of Judah were captives in Babylon, the capital city of the Neo-Babylonian Empire, following their defeat ...

, this month is called

Nisan Nisan (or Nissan; he, נִיסָן, Standard ''Nīsan'', Tiberian ''Nīsān''; from akk, 𒊬𒊒𒄀 ''Nisanu'') in the Babylonian and Hebrew calendars is the month of the barley ripening and first month of spring. The name of the month i ...

, and it is calculated based on mathematical rules designed to ensure that festivals are observed in their traditional season. Passover always falls in the springtime. This fixed lunisolar calendar follows rules introduced by

Hillel II Hillel II (Hebrew: הלל נשיאה, Hillel the Nasi), also known simply as Hillel, was an '' amora'' of the fifth generation in the Land of Israel. He held the office of '' Nasi'' of the Sanhedrin between 320 and 385 CE. He was the son and succ ...

and refined until the ninth century This calculation makes use of a mean lunation length used by

Ptolemy Claudius Ptolemy (; grc-gre, Πτολεμαῖος, ; la, Claudius Ptolemaeus; AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of importanc ...

and handed down from Babylonians, which is still very accurate: ca. 29.530594 days vs. a present value (see

below Below may refer to: *Earth *Ground (disambiguation) *Soil *Floor *Bottom (disambiguation) *Less than *Temperatures below freezing *Hell or underworld People with the surname *Ernst von Below (1863–1955), German World War I general *Fred Below ( ...

) of 29.530589 days. This difference of only 0.000005, or five-millionths of a day, adds up to about only four hours since Babylonian times. The messianic

Pentecostal Pentecostalism or classical Pentecostalism is a Protestantism, Protestant Charismatic Christianity, Charismatic Christian movementNew Israelites of Peru, keeps the new moon as a Sabbath of rest. As an evangelical church, it follows the Bible's teachings that God sanctified the

seventh-day Sabbath The seventh-day Sabbath, observed from Friday evening to Saturday evening, is an important part of the beliefs and practices of seventh-day churches. These churches emphasize biblical references such as the ancient Hebrew practice of beginning a ...

, and the new moons in addition to it. No work may be done from dusk until dusk, and the services run for 11 hours, although a large number spend 24 hours within the gates of the temples, sleeping and singing praises throughout the night.

Chinese calendar

The new moon is the beginning of the month in the

. Some Buddhist Chinese keep a vegetarian diet on the new moon and full moon each month.

Hindu calendar

The new moon is significant in the lunar

Hindu calendar The Hindu calendar, Panchanga () or Panjika 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 ...

. The first day of the calendar starts the day after the dark moon phase (

Amavasya Amāvásyā () is the lunar phase of the new moon in Sanskrit. Indian calendars use 30 lunar phases, called tithi in India. The dark moon tithi is when the Moon is within 12 degrees of the angular distance between the Sun and Moon before conjun ...

). There are fifteen moon dates for each of the waxing and waning periods. These fifteen dates are divided evenly into five categories: Nanda, Bhadra', Jaya, Rikta, and Purna, which are cycled through in that order. Nanda dates are considered to be favorable for auspicious works; Bhadra dates for works related to community, social, family, and friends; and Jaya dates for dealing with conflict. Rikta dates are considered beneficial only for works related to cruelty. Purna dates are considered to be favorable for all work.

Babylonian calendar The Babylonian calendar was a lunisolar calendar with years consisting of 12 lunar months, each beginning when a new crescent moon was first sighted low on the western horizon at sunset, plus an intercalary month inserted as needed by decree. Th ...

Lunar calendars

Islamic calendar

The

lunar Hijri calendar The Hijri calendar ( ar, ٱلتَّقْوِيم ٱلْهِجْرِيّ, translit=al-taqwīm al-hijrī), also known in English as the Muslim calendar and Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or ...

has exactly 12 lunar months in a year of 354 or 355 days. It has retained an observational definition of the new moon, marking the new month when the first crescent moon is seen, and making it impossible to be certain in advance of when a specific month will begin (in particular, the exact date on which the month of Ramadan will begin is not known in advance). In

Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in Western Asia. It covers the bulk of the Arabian Peninsula, and has a land area of about , making it the fifth-largest country in Asia, the second-largest in the Ara ...

, the new King Abdullah Centre for Crescent Observations and Astronomy in Mecca has a clock for addressing this as an international scientific project. In

Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...

, there is a "Central Ruet-e-Hilal Committee" whose head is Mufti Muneeb-ur-Rehman, assisted by 150 observatories of the

Pakistan Meteorological Department The Pakistan Meteorological Department (PMD) ( ur, , also known as Pakistan Met Office), is an autonomous and independent institution tasked with providing weather forecasts and public warnings concerning weather for protection, safety and gener ...

, which announces the sighting of the new moon. An attempt to unify Muslims on a scientifically calculated worldwide calendar was adopted by both the

Fiqh Council of North America The Fiqh Council of North America (originally known as ISNA Fiqh Committee) is an association of Muslims who interpret Islamic law on the North American continent. The FCNA was founded in 1986 with the goal of developing legal methodologies for ad ...

and the

European Council for Fatwa and Research The European Council for Fatwa and Research (ECFR) is a Dublin-based private foundation, founded in London on 29–30 March 1997 on the initiative of the Federation of Islamic Organizations in Europe. The council is a largely self-selected body, co ...

in 2007. The new calculation requires that conjunction must occur before sunset in Mecca, Saudi Arabia, and that, on the same evening, moonset must take place after sunset. These can be precisely calculated and therefore a unified calendar is possible should it become adopted worldwide.

Solar calendars holding moveable feasts

Baháʼí calendar

The

Baháʼí calendar The Badíʻ 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. Perfection, Mercy ...

is a solar calendar with certain new moons observed as moveable feasts. In the

Baháʼí Faith The Baháʼí Faith is a religion founded in the 19th century that teaches the essential worth of all religions and the unity of all people. Established by Baháʼu'lláh in the 19th century, it initially developed in Iran and parts of the ...

, effective from 2015 onwards, the "

Twin Holy Birthdays The Festivals of the Twin Birthdays or the Twin Holy Birthdays refers to two successive holy days in the Baháʼí calendar that celebrate the births of two central figures of the Baháʼí Faith. The two holy days are the birth of the Báb on t ...

", refer to two successive holy days in the

(the birth of the

Báb The Báb (b. ʿAlí Muḥammad; 20 October 1819 – 9 July 1850), was the messianic founder of Bábism, and one of the central figures of the Baháʼí Faith. He was a merchant from Shiraz in Qajar Iran who, in 1844 at the age of 25, claimed ...

and the

birth of Bahá'u'lláh Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the f ...

), will be observed on the first and the second day following the occurrence of the eighth new moon after Naw-Rúz (Baháʼí New Year), as determined in advance by astronomical tables using

Tehran Tehran (; fa, تهران ) is the largest city in Tehran Province and the capital of Iran. With a population of around 9 million in the city and around 16 million in the larger metropolitan area of Greater Tehran, Tehran is the most popul ...

as the point of reference.Momen, Moojan (2014)
The Badí` (Baháʼí) Calendar: An Introduction
This will result in the observance of the Twin Birthdays moving, year to year, from mid-October to mid-November according to the Gregorian calendar.

Christian liturgical calendar

Easter Easter,Traditional names for the feast in English are "Easter Day", as in the '' Book of Common Prayer''; "Easter Sunday", used by James Ussher''The Whole Works of the Most Rev. James Ussher, Volume 4'') and Samuel Pepys''The Diary of Samue ...

, the most important feast in the Christian

liturgical calendar The liturgical year, also called the church year, Christian year or kalendar, consists of the cycle of liturgical seasons in Christian churches that determines when feast days, including celebrations of saints, are to be observed, and which ...

, is a movable feast. The

date of Easter As a moveable feast, the date of Easter is determined in each year through a calculation known as (). Easter is celebrated on the first Sunday after the Paschal full moon, which is the first full moon on or after 21 March (a fixed approx ...

is determined by reference to the

ecclesiastical full moon An ecclesiastical full moon is formally the 14th day of the ecclesiastical lunar month (an ecclesiastical moon) in an ecclesiastical lunar calendar. The ecclesiastical lunar calendar spans the year with lunar months of 30 and 29 days which are int ...

, which, being historically difficult to determine with precision, is defined as being fourteen days after the (first crescent) new moon.

Notes

References

Works cited

* * * *

External links

Moon Watch site
of the Nautical Almanac Office {{DEFAULTSORT:New Moon Phases of the Moon