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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
Details and Options Details and Options
Examples  
Basic Examples  
Scope  
Dates  
Locations  
Options  
"SunAngleTest"  
Properties & Relations  
See Also
Related Guides
History
Cite this Page

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:

Wolfram Language code: DaylightQ[]

Determine if it is daylight for a specified date:

Wolfram Language code: DaylightQ[DateObject[{2023, 3, 20, 11, 0}, TimeZone -> -5]]

Determine if it is currently daylight for a specified location:

Wolfram Language code: DaylightQ[["Chicago"]]

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

Wolfram Language code: DaylightQ[GeoPosition[{50.3, -80.1}], DateObject[{2023, 10, 1, 11, 0}, "Minute", "Gregorian", -5.]]

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

Wolfram Language code: DaylightQ[["Saint Louis"], DateObject[{2023, 10, 1, 11, 0}, "Minute", "Gregorian", -5.]]

Scope  (8)

Dates  (3)

Dates can be specified as a DateObject:

Wolfram Language code: DaylightQ[DateObject[{2023, 9, 23, 15, 0}, TimeZone -> "America/Chicago"]]

Dates can be specified as a date string:

Wolfram Language code: DaylightQ["September 23, 2022 3:00PM CDT"]

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

Wolfram Language code: DaylightQ[DateRange[DateObject[{2023, 1, 1, 9, 0}, "Minute", "Gregorian", -5.], DateObject[{2023, 12, 31, 9, 0}, "Minute", "Gregorian", -5.], 10]]

Locations  (5)

Locations can be latitude/longitude pairs:

Wolfram Language code: DaylightQ[GeoPosition[{40.1, -88.2}]]

Locations can be relevant entities:

Wolfram Language code: DaylightQ[["Saint Louis"]]

Find the Sun's position for multiple locations:

Wolfram Language code: DaylightQ[{["Chicago"], ["Tokyo"]}]
Wolfram Language code: LocalTimeZone[Entity["City", {"Tokyo", "Tokyo", "Japan"}]]

Find the Sun's position for multiple locations on different dates:

Wolfram Language code: DaylightQ[{{Entity["City", {"Chicago", "Illinois", "UnitedStates"}], DateObject[{2025, 1, 1, 12}, "Hour", "Gregorian", "America/Chicago"]}, {Entity["City", {"Tokyo", "Tokyo", "Japan"}], DateObject[{2025, 3, 14, 18, 0, 0}, "Instant", "Gregorian", "Asia/Tokyo"]}}]

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

Wolfram Language code: DaylightQ[["Russia"], DateObject[{2022, 4, 2, 10}, "Hour", "Gregorian", -5.]]
Wolfram Language code: DaylightQ[["Russia"], DateObject[{2022, 4, 2, 10}, "Hour", "Gregorian", -5.], "Everywhere"]

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

Wolfram Language code: DaylightQ[["Russia"], DateObject[{2022, 4, 2, 10}, "Hour", "Gregorian", -5.], "Somewhere"]

Options  (1)

"SunAngleTest"  (1)

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

Wolfram Language code: DaylightQ[GeoPosition[{40.1, -88.2}], DateObject[{2014, 4, 22, 20, 0, 0}, "Instant", "Gregorian", -5.]]
Wolfram Language code: SunPosition[GeoPosition[{40.1, -88.2}], DateObject[{2014, 4, 22, 20, 0, 0}, "Instant", "Gregorian", -5.]]

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

Wolfram Language code: DaylightQ[GeoPosition[{40.1, -88.2}], DateObject[{2014, 4, 22, 19, 30, 0}, "Instant", "Gregorian", -5.], "SunAngleTest" -> (# > -10&)]

Properties & Relations  (1)

Find whether it is daylight for this location and date:

Wolfram Language code: loc = GeoPosition[{40.11, -88.22}]; date = DateObject[{2023, 7, 16, 12, 36, 0}];
Wolfram Language code: DaylightQ[loc, date]

It is daylight if the Sun has a positive altitude:

Wolfram Language code: SunPosition[loc, date]

This can also be computed using AstroPosition:

Wolfram Language code: AstroPosition[Entity["Star", "Sun"], {"Horizon", loc, date}]["Altitude"]
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_2026_daylightq, author="Wolfram Research", title="{DaylightQ}", year="2023", howpublished="\url{https://reference.wolfram.com/language/ref/DaylightQ.html}", note=[Accessed: 12-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_daylightq, organization={Wolfram Research}, title={DaylightQ}, year={2023}, url={https://reference.wolfram.com/language/ref/DaylightQ.html}, note=[Accessed: 12-June-2026]}