[edit] Last updated: Fri, 28 Jun 2013

date_sunset

(PHP 5)

date_sunset — Returns time of sunset for a given day and location

Description

mixed date_sunset ( int $timestamp [, int $format = SUNFUNCS_RET_STRING [, float $latitude = ini_get("date.default_latitude") [, float $longitude = ini_get("date.default_longitude") [, float $zenith = ini_get("date.sunset_zenith") [, float $gmt_offset = 0 ]]]]] )

date_sunset() returns the sunset time for a given day (specified as a timestamp) and location.

Parameters

timestamp

The timestamp of the day from which the sunset time is taken.

format

*`format`* constants
constant	description	example
SUNFUNCS_RET_STRING	returns the result as string	16:46
SUNFUNCS_RET_DOUBLE	returns the result as float	16.78243132
SUNFUNCS_RET_TIMESTAMP	returns the result as integer (timestamp)	1095034606

latitude

Defaults to North, pass in a negative value for South. See also: date.default_latitude

longitude

Defaults to East, pass in a negative value for West. See also: date.default_longitude

zenith

Default: date.sunset_zenith

gmtoffset

Specified in hours.

Errors/Exceptions

Every call to a date/time function will generate a E_NOTICE if the time zone is not valid, and/or a E_STRICT or E_WARNING message if using the system settings or the TZ environment variable. See also date_default_timezone_set()

Changelog

Version	Description
5.1.0	Now issues the `E_STRICT` and `E_NOTICE` time zone errors.

Return Values

Returns the sunset time in a specified format on success or FALSE on failure.

Examples

Example #1 date_sunset() example


<?php

/* calculate the sunset time for Lisbon, Portugal
Latitude: 38.4 North
Longitude: 9 West
Zenith ~= 90
offset: +1 GMT
*/

echo date("D M d Y"). ', sunset time : ' .date_sunset(time(), SUNFUNCS_RET_STRING, 38.4, -9, 90, 1);

?>

The above example will output something similar to:

Mon Dec 20 2004, sunset time : 18:13


I use an IP to location database to determine the visitor's approximate latitude and longitude and then serve them a day or night color scheme based on whether it is before civil dawn or dusk. I've had problems when not specifying the timezone, specifically a 1 hour error, so I use GMT.





<?php


date_default_timezone_set("GMT");





function scheme() {


        $sunrise = date_sunrise(time(), SUNFUNCS_RET_DOUBLE, $latitude, $longitude, 96, 0);


        $sunset = date_sunset(time(), SUNFUNCS_RET_DOUBLE, $latitude, $longitude, 96, 0);


        $now = date("H") + date("i") / 60 + date("s") / 3600;





        if ($sunrise < $sunset)


                if (($now > $sunrise) && ($now < $sunset)) return "day";


                else return "night";


        else


                if (($now > $sunrise) || ($now < $sunset)) return "day";


                else return "night";


}


?>

down

-1

djwice at [the same] dot com ¶

8 years ago


A way to use this:



<?php



// De Bilt, The Netherlands, weather station #06260

$lat = 52.10;    // North

$long = 5.18;    // East

$offset = 1;    // difference between GMT and local time in hours



$zenith=90+50/60;

echo "<br><p>Sunrise: ".date_sunrise(time(), SUNFUNCS_RET_STRING, $lat, $long, $zenith, $offset);

echo "<br>Sunset: ".date_sunset(time(), SUNFUNCS_RET_STRING, $lat, $long, $zenith, $offset);



$zenith=96;

echo "<br><p>\"Civilian Twilight\" start: ".date_sunrise(time(), SUNFUNCS_RET_STRING, $lat, $long, $zenith, $offset);

echo "<br>\"Civilian Twilight\" end: ".date_sunset(time(), SUNFUNCS_RET_STRING, $lat, $long, $zenith, $offset);



$zenith=102;

echo "<br><p>\"Nautical Twilight\" start: ".date_sunrise(time(), SUNFUNCS_RET_STRING, $lat, $long, $zenith, $offset);

echo "<br>\"Nautical Twilight\" end: ".date_sunset(time(), SUNFUNCS_RET_STRING, $lat, $long, $zenith, $offset);



$zenith=108;

echo "<br><p>\"Astronomical Twilight\" start: ".date_sunrise(time(), SUNFUNCS_RET_STRING, $lat, $long, $zenith, $offset);

echo "<br>\"Astronomical Twilight\" end: ".date_sunset(time(), SUNFUNCS_RET_STRING, $lat, $long, $zenith, $offset);



?>  



Thanks to George King.

More sources about this topic:



http://www.qarlos.free.fr/navegacion/Sextante/formulas.htm

http://williams.best.vwh.net/sunrise_sunset_algorithm.htm

http://www.kevinboone.com/suntimes.html

http://star-www.st-and.ac.uk/~fv/webnotes/chapt12.htm

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