# LunationNumber

returns the number of new moons since the first new moon of the year 2000.

LunationNumber[date]

returns the number of new moons since the given date.

LunationNumber[scheme,date]

returns the number of new moons since the zeroth new moon of the given counting scheme.

# Details

• Lunations are periods between a new moon and a new moon, and are also known as synodic months.
• LunationNumber is a way to tell time by the motion of the Moon, effectively counting months.
• The result of LunationNumber is a real number. The integer part gives the number of new moons since the first new moon on January 6, 2000. The fractional part of a lunation number gives the phase of the Moon:
•  0 new moon 0.25 first quarter 0.5 full moon 0.75 last quarter
• The result of LunationNumber is proportional to the difference in ecliptic longitudes between the Sun and the Moon.
• Possible counting schemes include:
•  Automatic lunation 0 on January 6, 2000 "BrownLunationNumber" lunation 1 on January 17, 1923 "GoldstineLunationNumber" lunation 0 on January 1, –1001, proleptic Gregorian "HebrewLunationNumber" lunation 1 on September 6, –3761, proleptic Gregorian "IslamicLunationNumber" lunation 1 on July 17, 622, proleptic Gregorian "ThaiLunationNumber" lunation 0 on March 24, 638, proleptic Gregorian

# Examples

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## Basic Examples(3)

Find the current lunation number:

Find the lunation number of the beginning of the year 2020:

Find the current lunation number in the Islamic counting scheme:

## Scope(2)

Find the lunation number of a given date:

Find the lunation number of a date in a non-default scheme:

## Properties & Relations(4)

LunationNumber and FromLunationNumber are inverse functions:

New moons correspond to integer lunation numbers:

Full moons correspond to semi-integer lunation numbers:

Every solar eclipse happens within a few minutes of a new moon. Hence solar eclipses have an associated lunation number:

It is very close to the lunation number of the instant of maximum eclipse:

Wolfram Research (2023), LunationNumber, Wolfram Language function, https://reference.wolfram.com/language/ref/LunationNumber.html.

#### Text

Wolfram Research (2023), LunationNumber, Wolfram Language function, https://reference.wolfram.com/language/ref/LunationNumber.html.

#### CMS

Wolfram Language. 2023. "LunationNumber." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/LunationNumber.html.

#### APA

Wolfram Language. (2023). LunationNumber. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/LunationNumber.html

#### BibTeX

@misc{reference.wolfram_2024_lunationnumber, author="Wolfram Research", title="{LunationNumber}", year="2023", howpublished="\url{https://reference.wolfram.com/language/ref/LunationNumber.html}", note=[Accessed: 29-May-2024 ]}

#### BibLaTeX

@online{reference.wolfram_2024_lunationnumber, organization={Wolfram Research}, title={LunationNumber}, year={2023}, url={https://reference.wolfram.com/language/ref/LunationNumber.html}, note=[Accessed: 29-May-2024 ]}