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DaylightQ
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DaylightQ

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

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DaylightQ[datespec]

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

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DaylightQ[locationspec]

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

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DaylightQ[locationspec,datespec]

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

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

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

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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

open allclose all

Basic Examples  (5)Summary of the most common use cases

Determine if it is currently daylight for your location:

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-etsbfd
Out[1]=1

Determine if it is daylight for a specified date:

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-tu106
Out[1]=1

Determine if it is currently daylight for a specified location:

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-er85w0
Out[1]=1

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

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-k5huuj
Out[1]=1

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

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-bild8d
Out[1]=1

Scope  (7)Survey of the scope of standard use cases

Dates  (3)

Dates can be specified as a DateObject:

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-o50xxn
Out[1]=1

Dates can be specified as a date string:

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-zbahi
Out[1]=1

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

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-glueuf
Out[1]=1

Locations  (4)

Locations can be latitude/longitude pairs:

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-mmgexd
Out[1]=1

Locations can be relevant entities:

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-qurz1v
Out[1]=1

Find the Sun's position for multiple locations:

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-ckzkp2
Out[1]=1

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

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-73hr7a
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0c0qneqogdxvn-t8k9ku
Out[2]=2

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

In[3]:=3
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https://wolfram.com/xid/0c0qneqogdxvn-l1ug38
Out[3]=3

Options  (1)Common values & functionality for each option

"SunAngleTest"  (1)

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

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-hpekom
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0c0qneqogdxvn-be60yx
Out[2]=2

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

In[3]:=3
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https://wolfram.com/xid/0c0qneqogdxvn-drspcx
Out[3]=3

Properties & Relations  (1)Properties of the function, and connections to other functions

Find whether it is daylight for this location and date:

In[1]:=1
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https://wolfram.com/xid/0c0qneqogdxvn-knatob
In[3]:=3
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https://wolfram.com/xid/0c0qneqogdxvn-iof97i
Out[3]=3

It is daylight if the Sun has a positive altitude:

In[4]:=4
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https://wolfram.com/xid/0c0qneqogdxvn-ebsryo
Out[4]=4

This can also be computed using AstroPosition:

In[5]:=5
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https://wolfram.com/xid/0c0qneqogdxvn-hyasq8
Out[5]=5
Wolfram Research (2014), DaylightQ, Wolfram Language function, https://reference.wolfram.com/language/ref/DaylightQ.html (updated 2023).
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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).

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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.

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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

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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: 23-June-2025 ]}

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@misc{reference.wolfram_2025_daylightq, author="Wolfram Research", title="{DaylightQ}", year="2023", howpublished="\url{https://reference.wolfram.com/language/ref/DaylightQ.html}", note=[Accessed: 23-June-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: 23-June-2025 ]}

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@online{reference.wolfram_2025_daylightq, organization={Wolfram Research}, title={DaylightQ}, year={2023}, url={https://reference.wolfram.com/language/ref/DaylightQ.html}, note=[Accessed: 23-June-2025 ]}