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A sunrise/sunset calculator.

View SolarInfo.cs
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using System;
using System.Diagnostics;
 
namespace SunriseCalculator
{
public class SolarInfo
{
public double SolarDeclination { get; private set; }
public TimeSpan EquationOfTime { get; private set; }
public DateTime Sunrise { get; private set; }
public DateTime Sunset { get; private set; }
public TimeSpan? Noon { get; private set; }
public DateTime Date { get; private set; }
 
private SolarInfo() {}
 
public static SolarInfo ForDate(double latitude, double longitude, DateTime date)
{
var info = new SolarInfo();
info.Date = date = date.Date;
 
var year = date.Year;
var month = date.Month;
var day = date.Day;
if ((latitude >= -90) && (latitude < -89))
{
//alert("All latitudes between 89 and 90 S\n will be set to -89");
//latLongForm["latDeg"].value = -89;
latitude = -89;
}
 
if ((latitude <= 90) && (latitude > 89))
{
//alert("All latitudes between 89 and 90 N\n will be set to 89");
//latLongForm["latDeg"].value = 89;
latitude = 89;
}
 
//***** Calculate the time of sunrise
var JD = calcJD(year, month, day);
//var dow = calcDayOfWeek(JD);
var doy = calcDayOfYear(month, day, isLeapYear(year));
var T = calcTimeJulianCent(JD);
 
// var alpha = calcSunRtAscension(T);
var solarDec = calcSunDeclination(T);
var eqTime = calcEquationOfTime(T); // (in minutes)
 
 
 
// Calculate sunrise for this date
// if no sunrise is found, set flag nosunrise
var nosunrise = false;
 
var riseTimeGMT = calcSunriseUTC(JD, latitude, longitude);
nosunrise = !isNumber(riseTimeGMT);
 
// Calculate sunset for this date
// if no sunset is found, set flag nosunset
var nosunset = false;
var setTimeGMT = calcSunsetUTC(JD, latitude, longitude);
if (!isNumber(setTimeGMT))
{
nosunset = true;
}
 
if (!nosunrise) // Sunrise was found
{
info.Sunrise = date.Date.AddMinutes(riseTimeGMT);
}
 
if (!nosunset) // Sunset was found
{
info.Sunset = date.Date.AddMinutes(setTimeGMT);
}
 
// Calculate solar noon for this date
var solNoonGMT = calcSolNoonUTC(T, longitude);
 
if (!(nosunset || nosunrise))
{
info.Noon = TimeSpan.FromMinutes(solNoonGMT);
}
 
 
var tsnoon = calcTimeJulianCent(calcJDFromJulianCent(T) - 0.5 + solNoonGMT / 1440.0);
eqTime = calcEquationOfTime(tsnoon);
solarDec = calcSunDeclination(tsnoon);
 
info.EquationOfTime = TimeSpan.FromMinutes(eqTime);
info.SolarDeclination = solarDec;
 
// report special cases of no sunrise
if (nosunrise)
{
// if Northern hemisphere and spring or summer, OR
// if Southern hemisphere and fall or winter, use
// previous sunrise and next sunset
 
if (((latitude > 66.4) && (doy > 79) && (doy < 267)) ||
((latitude < -66.4) && ((doy < 83) || (doy > 263))))
{
var newjd = findRecentSunrise(JD, latitude, longitude);
var newtime = calcSunriseUTC(newjd, latitude, longitude);
 
if (newtime > 1440)
{
newtime -= 1440;
newjd += 1.0;
}
if (newtime < 0)
{
newtime += 1440;
newjd -= 1.0;
}
 
info.Sunrise = ConvertToDate(newtime, newjd);
}
 
// if Northern hemisphere and fall or winter, OR
// if Southern hemisphere and spring or summer, use
// next sunrise and previous sunset
 
else if (((latitude > 66.4) && ((doy < 83) || (doy > 263))) ||
((latitude < -66.4) && (doy > 79) && (doy < 267)))
{
var newjd = findNextSunrise(JD, latitude, longitude);
var newtime = calcSunriseUTC(newjd, latitude, longitude);
 
if (newtime > 1440)
{
newtime -= 1440;
newjd += 1.0;
}
if (newtime < 0)
{
newtime += 1440;
newjd -= 1.0;
}
 
info.Sunrise = ConvertToDate(newtime, newjd);
}
else
{
Debug.Fail("Cannot Find Sunrise!");
}
 
// alert("Last Sunrise was on day " + findRecentSunrise(JD, latitude, longitude));
// alert("Next Sunrise will be on day " + findNextSunrise(JD, latitude, longitude));
}
 
if (nosunset)
{
// if Northern hemisphere and spring or summer, OR
// if Southern hemisphere and fall or winter, use
// previous sunrise and next sunset
 
if (((latitude > 66.4) && (doy > 79) && (doy < 267)) ||
((latitude < -66.4) && ((doy < 83) || (doy > 263))))
{
var newjd = findNextSunset(JD, latitude, longitude);
var newtime = calcSunsetUTC(newjd, latitude, longitude);
 
if (newtime > 1440)
{
newtime -= 1440;
newjd += 1.0;
}
if (newtime < 0)
{
newtime += 1440;
newjd -= 1.0;
}
 
info.Sunset = ConvertToDate(newtime, newjd);
}
 
// if Northern hemisphere and fall or winter, OR
// if Southern hemisphere and spring or summer, use
// next sunrise and last sunset
 
else if (((latitude > 66.4) && ((doy < 83) || (doy > 263))) ||
((latitude < -66.4) && (doy > 79) && (doy < 267)))
{
var newjd = findRecentSunset(JD, latitude, longitude);
var newtime = calcSunsetUTC(newjd, latitude, longitude);
 
if (newtime > 1440)
{
newtime -= 1440;
newjd += 1.0;
}
if (newtime < 0)
{
newtime += 1440;
newjd -= 1.0;
}
 
info.Sunset = ConvertToDate(newtime, newjd);
}
else
{
Debug.Fail("Cannot Find Sunset!");
}
 
}
 
return info;
}
 
// This is inspired by timeStringShortAMPM from the original source.
/// <summary>Note: This treats fractional julian days as whole days, so the minutes portion of the julian day will be replaced with the value of the minutes parameter.</summary>
private static DateTime ConvertToDate(double minutes, double JD)
{
var julianday = JD;
var floatHour = minutes / 60.0;
var hour = Math.Floor(floatHour);
var floatMinute = 60.0 * (floatHour - Math.Floor(floatHour));
var minute = Math.Floor(floatMinute);
var floatSec = 60.0 * (floatMinute - Math.Floor(floatMinute));
var second = Math.Floor(floatSec + 0.5);
 
minute += (second >= 30) ? 1 : 0;
 
if (minute >= 60)
{
minute -= 60;
hour++;
}
 
if (hour > 23)
{
hour -= 24;
julianday += 1.0;
}
 
if (hour < 0)
{
hour += 24;
julianday -= 1.0;
}
 
return calcDayFromJD(julianday).Add(new TimeSpan(0, (int)hour, (int)minute, (int)second));
}
 
private static DateTime calcDayFromJD(double jd)
{
var z = Math.Floor(jd + 0.5);
var f = (jd + 0.5) - z;
 
double A = 0;
if (z < 2299161)
{
A = z;
}
else
{
var alpha = Math.Floor((z - 1867216.25) / 36524.25);
A = z + 1 + alpha - Math.Floor(alpha / 4);
}
 
var B = A + 1524;
var C = Math.Floor((B - 122.1) / 365.25);
var D = Math.Floor(365.25 * C);
var E = Math.Floor((B - D) / 30.6001);
 
var day = B - D - Math.Floor(30.6001 * E) + f;
var month = (E < 14) ? E - 1 : E - 13;
var year = (month > 2) ? C - 4716 : C - 4715;
 
return new DateTime((int)year, (int)month, (int)day, 0, 0, 0, DateTimeKind.Utc);
}
 
private static bool isLeapYear(int yr)
{
return ((yr % 4 == 0 && yr % 100 != 0) || yr % 400 == 0);
}
 
 
//*********************************************************************/
 
// isPosInteger returns false if the value is not a positive integer, true is
// returned otherwise. The code is from taken from Danny Goodman's Javascript
// Handbook, p. 372.
 
private static bool isPosInteger(int inputVal)
{
return inputVal > 0;
}
 
private static bool isNumber(double inputVal)
{
//var oneDecimal = false;
//var inputStr = "" + inputVal;
//for (var i = 0; i < inputStr.length; i++)
//{
// var oneChar = inputStr.charAt(i);
// if (i == 0 && (oneChar == "-" || oneChar == "+"))
// {
// continue;
// }
// if (oneChar == "." && !oneDecimal)
// {
// oneDecimal = true;
// continue;
// }
// if (oneChar < "0" || oneChar > "9")
// {
// return false;
// }
//}
//return true;
 
// TODO: Make sure I ported this function correctly
return !double.IsNaN(inputVal);
}
 
// Convert radian angle to degrees
private static double radToDeg(double angleRad)
{
return (180.0 * angleRad / Math.PI);
}
 
 
// Convert degree angle to radians
private static double degToRad(double angleDeg)
{
return (Math.PI * angleDeg / 180.0);
}
 
//***********************************************************************/
//* Name: calcDayOfYear */
//* Type: Function */
//* Purpose: Finds numerical day-of-year from mn, day and lp year info */
//* Arguments: */
//* month: January = 1 */
//* day : 1 - 31 */
//* lpyr : 1 if leap year, 0 if not */
//* Return value: */
//* The numerical day of year */
//***********************************************************************/
private static int calcDayOfYear(int mn, int dy, bool lpyr)
{
var k = (lpyr ? 1 : 2);
var doy = Math.Floor((275d * mn) / 9d) - k * Math.Floor((mn + 9d) / 12d) + dy - 30;
return (int)doy;
}
 
 
//***********************************************************************/
//* Name: calcDayOfWeek */
//* Type: Function */
//* Purpose: Derives weekday from Julian Day */
//* Arguments: */
//* juld : Julian Day */
//* Return value: */
//* String containing name of weekday */
//***********************************************************************/
private static string calcDayOfWeek(double juld)
{
var A = (juld + 1.5) % 7;
var DOW = (A == 0) ? "Sunday" : (A == 1) ? "Monday" : (A == 2) ? "Tuesday" : (A == 3) ? "Wednesday" : (A == 4) ? "Thursday" : (A == 5) ? "Friday" : "Saturday";
return DOW;
}
 
//***********************************************************************/
//* Name: calcJD */
//* Type: Function */
//* Purpose: Julian day from calendar day */
//* Arguments: */
//* year : 4 digit year */
//* month: January = 1 */
//* day : 1 - 31 */
//* Return value: */
//* The Julian day corresponding to the date */
//* Note: */
//* Number is returned for start of day. Fractional days should be */
//* added later. */
//***********************************************************************/
private static double calcJD(int year, int month, int day)
{
if (month <= 2)
{
year -= 1;
month += 12;
}
 
var A = Math.Floor(year / 100d);
var B = 2 - A + Math.Floor(A / 4d);
 
var JD = Math.Floor(365.25 * (year + 4716)) + Math.Floor(30.6001 * (month + 1.0)) + day + B - 1524.5;
 
return JD;
}
 
//***********************************************************************/
//* Name: calcTimeJulianCent */
//* Type: Function */
//* Purpose: convert Julian Day to centuries since J2000.0. */
//* Arguments: */
//* jd : the Julian Day to convert */
//* Return value: */
//* the T value corresponding to the Julian Day */
//***********************************************************************/
private static double calcTimeJulianCent(double jd)
{
var T = (jd - 2451545.0) / 36525.0;
return T;
}
 
 
//***********************************************************************/
//* Name: calcJDFromJulianCent */
//* Type: Function */
//* Purpose: convert centuries since J2000.0 to Julian Day. */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* the Julian Day corresponding to the t value */
//***********************************************************************/
private static double calcJDFromJulianCent(double t)
{
var JD = t * 36525.0 + 2451545.0;
return JD;
}
 
//***********************************************************************/
//* Name: calGeomMeanLongSun */
//* Type: Function */
//* Purpose: calculate the Geometric Mean Longitude of the Sun */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* the Geometric Mean Longitude of the Sun in degrees */
//***********************************************************************/
private static double calcGeomMeanLongSun(double t)
{
var L0 = 280.46646 + t * (36000.76983 + 0.0003032 * t);
while (L0 > 360.0)
{
L0 -= 360.0;
}
while (L0 < 0.0)
{
L0 += 360.0;
}
return L0; // in degrees
}
 
//***********************************************************************/
//* Name: calGeomAnomalySun */
//* Type: Function */
//* Purpose: calculate the Geometric Mean Anomaly of the Sun */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* the Geometric Mean Anomaly of the Sun in degrees */
//***********************************************************************/
private static double calcGeomMeanAnomalySun(double t)
{
var M = 357.52911 + t * (35999.05029 - 0.0001537 * t);
return M; // in degrees
}
 
 
//***********************************************************************/
//* Name: calcEccentricityEarthOrbit */
//* Type: Function */
//* Purpose: calculate the eccentricity of earth's orbit */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* the unitless eccentricity */
//***********************************************************************/
private static double calcEccentricityEarthOrbit(double t)
{
var e = 0.016708634 - t * (0.000042037 + 0.0000001267 * t);
return e; // unitless
}
 
//***********************************************************************/
//* Name: calcSunEqOfCenter */
//* Type: Function */
//* Purpose: calculate the equation of center for the sun */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* in degrees */
//***********************************************************************/
private static double calcSunEqOfCenter(double t)
{
var m = calcGeomMeanAnomalySun(t);
 
var mrad = degToRad(m);
var sinm = Math.Sin(mrad);
var sin2m = Math.Sin(mrad + mrad);
var sin3m = Math.Sin(mrad + mrad + mrad);
 
var C = sinm * (1.914602 - t * (0.004817 + 0.000014 * t)) + sin2m * (0.019993 - 0.000101 * t) + sin3m * 0.000289;
return C; // in degrees
}
 
//***********************************************************************/
//* Name: calcSunTrueLong */
//* Type: Function */
//* Purpose: calculate the true longitude of the sun */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* sun's true longitude in degrees */
//***********************************************************************/
private static double calcSunTrueLong(double t)
{
var l0 = calcGeomMeanLongSun(t);
var c = calcSunEqOfCenter(t);
 
var O = l0 + c;
return O; // in degrees
}
 
//***********************************************************************/
//* Name: calcSunTrueAnomaly */
//* Type: Function */
//* Purpose: calculate the true anamoly of the sun */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* sun's true anamoly in degrees */
//***********************************************************************/
private static double calcSunTrueAnomaly(double t)
{
var m = calcGeomMeanAnomalySun(t);
var c = calcSunEqOfCenter(t);
 
var v = m + c;
return v; // in degrees
}
 
 
 
//***********************************************************************/
//* Name: calcSunRadVector */
//* Type: Function */
//* Purpose: calculate the distance to the sun in AU */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* sun radius vector in AUs */
//***********************************************************************/
private static double calcSunRadVector(double t)
{
var v = calcSunTrueAnomaly(t);
var e = calcEccentricityEarthOrbit(t);
 
var R = (1.000001018 * (1 - e * e)) / (1 + e * Math.Cos(degToRad(v)));
return R; // in AUs
}
 
 
 
//***********************************************************************/
//* Name: calcSunApparentLong */
//* Type: Function */
//* Purpose: calculate the apparent longitude of the sun */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* sun's apparent longitude in degrees */
//***********************************************************************/
private static double calcSunApparentLong(double t)
{
var o = calcSunTrueLong(t);
 
var omega = 125.04 - 1934.136 * t;
var lambda = o - 0.00569 - 0.00478 * Math.Sin(degToRad(omega));
return lambda; // in degrees
}
 
 
 
//***********************************************************************/
//* Name: calcMeanObliquityOfEcliptic */
//* Type: Function */
//* Purpose: calculate the mean obliquity of the ecliptic */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* mean obliquity in degrees */
//***********************************************************************/
private static double calcMeanObliquityOfEcliptic(double t)
{
var seconds = 21.448 - t * (46.8150 + t * (0.00059 - t * (0.001813)));
var e0 = 23.0 + (26.0 + (seconds / 60.0)) / 60.0;
return e0; // in degrees
}
 
 
 
//***********************************************************************/
//* Name: calcObliquityCorrection */
//* Type: Function */
//* Purpose: calculate the corrected obliquity of the ecliptic */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* corrected obliquity in degrees */
//***********************************************************************/
private static double calcObliquityCorrection(double t)
{
var e0 = calcMeanObliquityOfEcliptic(t);
 
var omega = 125.04 - 1934.136 * t;
var e = e0 + 0.00256 * Math.Cos(degToRad(omega));
return e; // in degrees
}
 
//***********************************************************************/
//* Name: calcSunRtAscension */
//* Type: Function */
//* Purpose: calculate the right ascension of the sun */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* sun's right ascension in degrees */
//***********************************************************************/
private static double calcSunRtAscension(double t)
{
var e = calcObliquityCorrection(t);
var lambda = calcSunApparentLong(t);
 
var tananum = (Math.Cos(degToRad(e)) * Math.Sin(degToRad(lambda)));
var tanadenom = (Math.Cos(degToRad(lambda)));
var alpha = radToDeg(Math.Atan2(tananum, tanadenom));
return alpha; // in degrees
}
 
//***********************************************************************/
//* Name: calcSunDeclination */
//* Type: Function */
//* Purpose: calculate the declination of the sun */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* sun's declination in degrees */
//***********************************************************************/
private static double calcSunDeclination(double t)
{
var e = calcObliquityCorrection(t);
var lambda = calcSunApparentLong(t);
 
var sint = Math.Sin(degToRad(e)) * Math.Sin(degToRad(lambda));
var theta = radToDeg(Math.Asin(sint));
return theta; // in degrees
}
 
//***********************************************************************/
//* Name: calcEquationOfTime */
//* Type: Function */
//* Purpose: calculate the difference between true solar time and mean */
//* solar time */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* Return value: */
//* equation of time in minutes of time */
//***********************************************************************/
private static double calcEquationOfTime(double t)
{
var epsilon = calcObliquityCorrection(t);
var l0 = calcGeomMeanLongSun(t);
var e = calcEccentricityEarthOrbit(t);
var m = calcGeomMeanAnomalySun(t);
 
var y = Math.Tan(degToRad(epsilon) / 2.0);
y *= y;
 
var sin2l0 = Math.Sin(2.0 * degToRad(l0));
var sinm = Math.Sin(degToRad(m));
var cos2l0 = Math.Cos(2.0 * degToRad(l0));
var sin4l0 = Math.Sin(4.0 * degToRad(l0));
var sin2m = Math.Sin(2.0 * degToRad(m));
 
var Etime = y * sin2l0 - 2.0 * e * sinm + 4.0 * e * y * sinm * cos2l0
- 0.5 * y * y * sin4l0 - 1.25 * e * e * sin2m;
 
return radToDeg(Etime) * 4.0; // in minutes of time
}
 
//***********************************************************************/
//* Name: calcHourAngleSunrise */
//* Type: Function */
//* Purpose: calculate the hour angle of the sun at sunrise for the */
//* latitude */
//* Arguments: */
//* lat : latitude of observer in degrees */
//* solarDec : declination angle of sun in degrees */
//* Return value: */
//* hour angle of sunrise in radians */
//***********************************************************************/
private static double calcHourAngleSunrise(double lat, double solarDec)
{
var latRad = degToRad(lat);
var sdRad = degToRad(solarDec);
 
var HAarg = (Math.Cos(degToRad(90.833)) / (Math.Cos(latRad) * Math.Cos(sdRad)) - Math.Tan(latRad) * Math.Tan(sdRad));
var HA = (Math.Acos(Math.Cos(degToRad(90.833)) / (Math.Cos(latRad) * Math.Cos(sdRad)) - Math.Tan(latRad) * Math.Tan(sdRad)));
return HA; // in radians
}
 
//***********************************************************************/
//* Name: calcHourAngleSunset */
//* Type: Function */
//* Purpose: calculate the hour angle of the sun at sunset for the */
//* latitude */
//* Arguments: */
//* lat : latitude of observer in degrees */
//* solarDec : declination angle of sun in degrees */
//* Return value: */
//* hour angle of sunset in radians */
 
private static double calcHourAngleSunset(double lat, double solarDec)
{
var latRad = degToRad(lat);
var sdRad = degToRad(solarDec);
 
var HAarg = (Math.Cos(degToRad(90.833)) / (Math.Cos(latRad) * Math.Cos(sdRad)) - Math.Tan(latRad) * Math.Tan(sdRad));
 
var HA = (Math.Acos(Math.Cos(degToRad(90.833)) / (Math.Cos(latRad) * Math.Cos(sdRad)) - Math.Tan(latRad) * Math.Tan(sdRad)));
 
return -HA; // in radians
}
 
 
//***********************************************************************/
//* Name: calcSunriseUTC */
//* Type: Function */
//* Purpose: calculate the Universal Coordinated Time (UTC) of sunrise */
//* for the given day at the given location on earth */
//* Arguments: */
//* JD : julian day */
//* latitude : latitude of observer in degrees */
//* longitude : longitude of observer in degrees */
//* Return value: */
//* time in minutes from zero Z */
//***********************************************************************/
private static double calcSunriseUTC(double JD, double latitude, double longitude)
{
var t = calcTimeJulianCent(JD);
 
// *** Find the time of solar noon at the location, and use
// that declination. This is better than start of the
// Julian day
 
var noonmin = calcSolNoonUTC(t, longitude);
var tnoon = calcTimeJulianCent(JD + noonmin / 1440.0);
 
// *** First pass to approximate sunrise (using solar noon)
 
var eqTime = calcEquationOfTime(tnoon);
var solarDec = calcSunDeclination(tnoon);
var hourAngle = calcHourAngleSunrise(latitude, solarDec);
 
var delta = longitude - radToDeg(hourAngle);
var timeDiff = 4 * delta; // in minutes of time
var timeUTC = 720 + timeDiff - eqTime; // in minutes
 
// alert("eqTime = " + eqTime + "\nsolarDec = " + solarDec + "\ntimeUTC = " + timeUTC);
 
// *** Second pass includes fractional jday in gamma calc
 
var newt = calcTimeJulianCent(calcJDFromJulianCent(t) + timeUTC / 1440.0);
eqTime = calcEquationOfTime(newt);
solarDec = calcSunDeclination(newt);
hourAngle = calcHourAngleSunrise(latitude, solarDec);
delta = longitude - radToDeg(hourAngle);
timeDiff = 4 * delta;
timeUTC = 720 + timeDiff - eqTime; // in minutes
 
// alert("eqTime = " + eqTime + "\nsolarDec = " + solarDec + "\ntimeUTC = " + timeUTC);
 
return timeUTC;
}
 
//***********************************************************************/
//* Name: calcSolNoonUTC */
//* Type: Function */
//* Purpose: calculate the Universal Coordinated Time (UTC) of solar */
//* noon for the given day at the given location on earth */
//* Arguments: */
//* t : number of Julian centuries since J2000.0 */
//* longitude : longitude of observer in degrees */
//* Return value: */
//* time in minutes from zero Z */
//***********************************************************************/
 
private static double calcSolNoonUTC(double t, double longitude)
{
// First pass uses approximate solar noon to calculate eqtime
var tnoon = calcTimeJulianCent(calcJDFromJulianCent(t) + longitude / 360.0);
var eqTime = calcEquationOfTime(tnoon);
var solNoonUTC = 720 + (longitude * 4) - eqTime; // min
 
var newt = calcTimeJulianCent(calcJDFromJulianCent(t) - 0.5 + solNoonUTC / 1440.0);
 
eqTime = calcEquationOfTime(newt);
// var solarNoonDec = calcSunDeclination(newt);
solNoonUTC = 720 + (longitude * 4) - eqTime; // min
 
return solNoonUTC;
}
 
//***********************************************************************/
//* Name: calcSunsetUTC */
//* Type: Function */
//* Purpose: calculate the Universal Coordinated Time (UTC) of sunset */
//* for the given day at the given location on earth */
//* Arguments: */
//* JD : julian day */
//* latitude : latitude of observer in degrees */
//* longitude : longitude of observer in degrees */
//* Return value: */
//* time in minutes from zero Z */
//***********************************************************************/
private static double calcSunsetUTC(double JD, double latitude, double longitude)
{
var t = calcTimeJulianCent(JD);
 
// *** Find the time of solar noon at the location, and use
// that declination. This is better than start of the
// Julian day
 
var noonmin = calcSolNoonUTC(t, longitude);
var tnoon = calcTimeJulianCent(JD + noonmin / 1440.0);
 
// First calculates sunrise and approx length of day
 
var eqTime = calcEquationOfTime(tnoon);
var solarDec = calcSunDeclination(tnoon);
var hourAngle = calcHourAngleSunset(latitude, solarDec);
 
var delta = longitude - radToDeg(hourAngle);
var timeDiff = 4 * delta;
var timeUTC = 720 + timeDiff - eqTime;
 
// first pass used to include fractional day in gamma calc
 
var newt = calcTimeJulianCent(calcJDFromJulianCent(t) + timeUTC / 1440.0);
eqTime = calcEquationOfTime(newt);
solarDec = calcSunDeclination(newt);
hourAngle = calcHourAngleSunset(latitude, solarDec);
 
delta = longitude - radToDeg(hourAngle);
timeDiff = 4 * delta;
timeUTC = 720 + timeDiff - eqTime; // in minutes
 
return timeUTC;
}
 
//***********************************************************************/
//* Name: findRecentSunrise */
//* Type: Function */
//* Purpose: calculate the julian day of the most recent sunrise */
//* starting from the given day at the given location on earth */
//* Arguments: */
//* JD : julian day */
//* latitude : latitude of observer in degrees */
//* longitude : longitude of observer in degrees */
//* Return value: */
//* julian day of the most recent sunrise */
//***********************************************************************/
private static double findRecentSunrise(double jd, double latitude, double longitude)
{
var julianday = jd;
 
var time = calcSunriseUTC(julianday, latitude, longitude);
while (!isNumber(time))
{
julianday -= 1.0;
time = calcSunriseUTC(julianday, latitude, longitude);
}
 
return julianday;
}
 
 
//***********************************************************************/
//* Name: findRecentSunset */
//* Type: Function */
//* Purpose: calculate the julian day of the most recent sunset */
//* starting from the given day at the given location on earth */
//* Arguments: */
//* JD : julian day */
//* latitude : latitude of observer in degrees */
//* longitude : longitude of observer in degrees */
//* Return value: */
//* julian day of the most recent sunset */
//***********************************************************************/
private static double findRecentSunset(double jd, double latitude, double longitude)
{
var julianday = jd;
 
var time = calcSunsetUTC(julianday, latitude, longitude);
while (!isNumber(time))
{
julianday -= 1.0;
time = calcSunsetUTC(julianday, latitude, longitude);
}
 
return julianday;
}
 
 
//***********************************************************************/
//* Name: findNextSunrise */
//* Type: Function */
//* Purpose: calculate the julian day of the next sunrise */
//* starting from the given day at the given location on earth */
//* Arguments: */
//* JD : julian day */
//* latitude : latitude of observer in degrees */
//* longitude : longitude of observer in degrees */
//* Return value: */
//* julian day of the next sunrise */
//***********************************************************************/
private static double findNextSunrise(double jd, double latitude, double longitude)
{
var julianday = jd;
 
var time = calcSunriseUTC(julianday, latitude, longitude);
while (!isNumber(time))
{
julianday += 1.0;
 
time = calcSunriseUTC(julianday, latitude, longitude);
 
}
 
return julianday;
}
 
 
//***********************************************************************/
//* Name: findNextSunset */
//* Type: Function */
//* Purpose: calculate the julian day of the next sunset */
//* starting from the given day at the given location on earth */
//* Arguments: */
//* JD : julian day */
//* latitude : latitude of observer in degrees */
//* longitude : longitude of observer in degrees */
//* Return value: */
//* julian day of the next sunset */
//***********************************************************************/
private static double findNextSunset(double jd, double latitude, double longitude)
{
var julianday = jd;
 
var time = calcSunsetUTC(julianday, latitude, longitude);
while (!isNumber(time))
{
julianday += 1.0;
time = calcSunsetUTC(julianday, latitude, longitude);
}
 
return julianday;
}
}
}

Would you be willing to license this code for use under the MIT license?

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