MoonPhase

MoonPhase[]

gives moon phase fraction of illumination for the current date.

MoonPhase[datespec]

gives moon phase fraction of illumination for the specified date.

MoonPhase[property]

gives the property of the moon phase for the current date.

MoonPhase[datespec,property]

gives the property of the moon phase for the specified date.

Details

  • The phase of the Moon, also known as the lunar phase, describes the illumination of the lunar surface by the Sun as seen from Earth.
  • MoonPhase[] makes use of $TimeZone to determine your time zone.
  • datespec can be a DateObject expression, a TimeObject expression or a date string.
  • datespec is assumed to be in $TimeZone, unless it is a DateObject or TimeObject expression with an explicit TimeZone option value.
  • If datespec is a list of dates, then the results will be given as EventSeries or TimeSeries objects.
  • datespec can be specified as {start,end,increment} for compatibility with DateRange specifications.
  • MoonPhase["Fraction"] is equivalent to MoonPhase[].
  • MoonPhase can accept the following values for property:
  • "Fraction" or "IlluminationFraction"fraction of illumination, from 0 to 1
    "SignedFraction" or "SignedIlluminationFraction"signed fraction of illumination, from -1 to 1
    "PhaseAngle"lunation angle, from 0 to 2π
    "PhaseAngleFraction"fraction of lunation angle, from 0 to 1
    "Name"name of the moon phase
    "Icon"icon representing the moon phase
  • MoonPhase[…,Method"method"] specifies how moon phases are defined. Fraction of illumination, as observed from the center of the Earth, is used by default.
  • Possible settings for the Method option include:
  • "Illumination"phase defined by fraction of illumination of the Moon
    "EclipticLongitude"phase defined by Moon‐Sun ecliptic longitude difference

Examples

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Basic Examples  (4)

Find the Moon's current fraction of illumination:

Find the Moon's fraction of illumination on a specified date:

Find the name of the Moon's current phase:

Generate an icon of the Moon's current phase:

Scope  (7)

Dates can be specified as a DateObject:

Dates can be specified as a date string:

Results for a range of dates:

Generalizations & Extensions  (1)

IconData can accept the signed fraction of the moon phase as its second argument:

Options  (1)

Method  (1)

By default, MoonPhase uses illumination of the Moon by the Sun to compute properties:

Alternatively, use a method based on the ecliptic longitude difference between Moon and Sun:

Properties & Relations  (1)

By default, the date is specified by the current date:

Possible Issues  (1)

The names of moon phases are based on the illumination fraction value. On a given day, the name of the moon phase may change, depending on what time it is. For example, a full moon does not last a full day, so even if a full moon occurs on that day, you may have to change the time in order to get the phase you might expect:

Neat Examples  (1)

Create a moon calendar:

Wolfram Research (2014), MoonPhase, Wolfram Language function, https://reference.wolfram.com/language/ref/MoonPhase.html (updated 2025).

Text

Wolfram Research (2014), MoonPhase, Wolfram Language function, https://reference.wolfram.com/language/ref/MoonPhase.html (updated 2025).

CMS

Wolfram Language. 2014. "MoonPhase." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2025. https://reference.wolfram.com/language/ref/MoonPhase.html.

APA

Wolfram Language. (2014). MoonPhase. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/MoonPhase.html

BibTeX

@misc{reference.wolfram_2024_moonphase, author="Wolfram Research", title="{MoonPhase}", year="2025", howpublished="\url{https://reference.wolfram.com/language/ref/MoonPhase.html}", note=[Accessed: 20-January-2025 ]}

BibLaTeX

@online{reference.wolfram_2024_moonphase, organization={Wolfram Research}, title={MoonPhase}, year={2025}, url={https://reference.wolfram.com/language/ref/MoonPhase.html}, note=[Accessed: 20-January-2025 ]}