<?php
require_once("math.php");
/*
the algorithm used is at http://williams.best.vwh.net/sunrise_sunset_algorithm.htm
note that the algorithm is not mine, it's just something i found on the net.
*/
class sun {
function rise($date,$timezone,$latitude,$longitude,$zenith) {
//1. calculate day of year
$n=(int)date("z",$date);
//2. convert longitude to hour value and calculate an approximate time
$lnghour=$longitude/15;
$t=$n+((6-$lnghour)/24);
//3. calculate the sun's mean anomaly
$m=(0.9856*$t)-3.289;
//4. calculate the sun's true longitude
$l=$m+(1.916*sind($m))+(0.020*sind(2*$m))+282.634;
$l=fmod($l,360);
//5a. calculate the sun's right ascension
$ra=atand(0.91764*tand($l));
$ra=fmod($ra,360);
//5b. right ascension needs to be in the same quadrant as $l (sun's true longitude)
$lquadrant=floor($l/90)*90;
$raquadrant=floor($ra/90)*90;
$ra=$ra+($lquadrant-$raquadrant);
unset($lquadrant); //temporary variable, not needed anymore
unset($raquadrant); //temporary variable, not needed anymore
//5c. right ascension value needs to be converted into hours
$ra=$ra/15;
//6. calculate sun's declination
$sindec=0.39782 * sind($l);
$cosdec=cosd(asind($sindec));
//7a. calculate the sun's local hour angle
$cosh=(cosd($zenith)-($sindec*sind($latitude))) / ($cosdec*cosd($latitude));
if ($cosh>1) {
return NULL; //sun does not rise at this location on the specified date
}
//7b. finish calculating H and convert into hours
$h=360-acosd($cosh);
$h=$h/15;
//8. calculate local mean time of rising
$t=$h+$ra-(0.06571*$t)-6.622;
//9. adjust back to UTC
$ut=$t-$lnghour;
$ut=fmod($ut,24);
//10. convert UTC to local time zone of latitude/longitude
$localt=$ut+$timezone;
//calculation finished, return result as a unix date
return $date+$localt*60*60;
}
function set($date,$timezone,$latitude,$longitude,$zenith) {
//1. calculate day of year
$n=(int)date("z",$date);
//2. convert longitude to hour value and calculate an approximate time
$lnghour=$longitude/15;
$t=$n+((18-$lnghour)/24);
//3. calculate the sun's mean anomaly
$m=(0.9856*$t)-3.289;
//4. calculate the sun's true longitude
$l=$m+(1.916*sind($m))+(0.020*sind(2*$m))+282.634;
$l=fmod($l,360);
//5a. calculate the sun's right ascension
$ra=atand(0.91764*tand($l));
$ra=fmod($ra,360);
//5b. right ascension needs to be in the same quadrant as $l (sun's true longitude)
$lquadrant=floor($l/90)*90;
$raquadrant=floor($ra/90)*90;
$ra=$ra+($lquadrant-$raquadrant);
unset($lquadrant); //temporary variable, not needed anymore
unset($raquadrant); //temporary variable, not needed anymore
//5c. right ascension value needs to be converted into hours
$ra=$ra/15;
//6. calculate sun's declination
$sindec=0.39782 * sind($l);
$cosdec=cosd(asind($sindec));
//7a. calculate the sun's local hour angle
$cosh=(cosd($zenith)-($sindec*sind($latitude))) / ($cosdec*cosd($latitude));
if ($cosh < -1) {
return NULL; //sun does not set at this location on the specified date
}
//7b. finish calculating H and convert into hours
$h=acosd($cosh);
$h=$h/15;
//8. calculate local mean time of rising
$t=$h+$ra-(0.06571*$t)-6.622;
//9. adjust back to UTC
$ut=$t-$lnghour;
$ut=fmod($ut,24);
//10. convert UTC to local time zone of latitude/longitude
$localt=$ut+$timezone;
//calculation finished, return result as a unix date
return $date+$localt*60*60;
}
}
?>
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