DaylightQ

DaylightQ[]

gives True if it is currently daylight from the user's location.

DaylightQ[datespec]

gives True if it is daylight from the user's location on the specified datespec.

DaylightQ[locationspec]

gives True if it is currently daylight from the specified locationspec.

DaylightQ[locationspec,datespec]

gives True if it is daylight from the specified locationspec on the specified datespec.

DaylightQ[{{location1,date1},{location2,date2},…}]

gives True if it is daylight from the specified locations and dates.

DaylightQ[locationspec,datespec,inclusionspec]

gives True if it is daylight from the specified locationspec on the specified datespec taking inclusionspec into account.

Details and Options

  • For a given date, find out whether the Sun is illuminating a given location on Earth.
  • The observation location can be any point on the surface of a body in the solar system, defining the local horizon.
  • Locations can be specified as Entity objects, assuming they represent objects with geographic coordinates, or they can be latitude/longitude pairs, assuming degrees as units.
  • DaylightQ[] makes use of $GeoLocation and $TimeZone to determine your location and time zone.
  • datespec can be a DateObject expression, a TimeObject expression, a date string or a {y,m,d,h,m,s} date list.
  • datespec is assumed to be in $TimeZone, unless it is a DateObject or TimeObject expression with an explicit TimeZone option value.
  • locationspec and datespec can be either individual items or lists of them.
  • If datespec is a list of dates, then the results will contain EventSeries objects.
  • datespec can be specified as {start,end,increment} for compatibility with DateRange specifications.
  • DaylightQ[…,inclusionspec] is used to specify how much of the locationspec must be in daylight.
  • Possible settings for inclusionspec include:
  • "Everywhere"all of the locationspec must be in daylight
    "Somewhere"some of the locationspec must be in daylight
    "Nowhere"none of the locationspec must be in daylight
  • DaylightQ can accept the following option:
  • "SunAngleTest" (#>0&)function applied to the Sun altitude angle to determine if it is daylight

Examples

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Basic Examples  (5)

Determine if it is currently daylight for your location:

Determine if it is daylight for a specified date:

Determine if it is currently daylight for a specified location:

Determine if it is daylight for a specified latitude/longitude and date:

Determine if it is currently daylight for a specified city and date:

Scope  (7)

Dates  (3)

Dates can be specified as a DateObject:

Dates can be specified as a date string:

Generate an event series that checks for daylight every 10 days in a year:

Locations  (4)

Locations can be latitude/longitude pairs:

Locations can be relevant entities:

Find the Sun's position for multiple locations:

By default, extended locations must be fully in daylight in order to be True:

The default behavior can be overridden to allow only part of the extended location to be in daylight:

Options  (1)

"SunAngleTest"  (1)

By default, it is considered daylight if the altitude angle of the Sun is greater than 0:

The default behavior can be overridden to redefine what is meant by daylight:

Properties & Relations  (1)

Find whether it is daylight for this location and date:

It is daylight if the Sun has a positive altitude:

This can also be computed using AstroPosition:

Wolfram Research (2014), DaylightQ, Wolfram Language function, https://reference.wolfram.com/language/ref/DaylightQ.html (updated 2023).

Text

Wolfram Research (2014), DaylightQ, Wolfram Language function, https://reference.wolfram.com/language/ref/DaylightQ.html (updated 2023).

CMS

Wolfram Language. 2014. "DaylightQ." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2023. https://reference.wolfram.com/language/ref/DaylightQ.html.

APA

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

BibTeX

@misc{reference.wolfram_2025_daylightq, author="Wolfram Research", title="{DaylightQ}", year="2023", howpublished="\url{https://reference.wolfram.com/language/ref/DaylightQ.html}", note=[Accessed: 05-May-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_daylightq, organization={Wolfram Research}, title={DaylightQ}, year={2023}, url={https://reference.wolfram.com/language/ref/DaylightQ.html}, note=[Accessed: 05-May-2025 ]}