Pchp.Library.DateTimeFunctions.CalculateSunTime C# (CSharp) Method

        private static double CalculateSunTime(int day, double latitude, double longitude, double zenith, bool getSunrise)
        {
            double lngHour, t, M, L, Lx, RA, RAx, Lquadrant, RAquadrant, sinDec, cosDec, cosH, H, T, UT, UTx;

            // convert the longitude to hour value and calculate an approximate time
            lngHour = longitude / 15;

            if (getSunrise)
                t = (double)day + ((6 - lngHour) / 24);
            else
                t = (double)day + ((18 - lngHour) / 24);

            // calculate the sun's mean anomaly:
            M = (0.9856 * t) - 3.289;

            // step 4: calculate the sun's true longitude:
            L = M + (1.916 * Math.Sin(ToRadians(M))) + (0.020 * Math.Sin(ToRadians(2 * M))) + 282.634;

            while (L < 0)
            {
                Lx = L + 360;
                Debug.Assert(Lx != L);
                L = Lx;
            }

            while (L >= 360)
            {
                Lx = L - 360;
                Debug.Assert(Lx != L);
                L = Lx;
            }

            // calculate the sun's right ascension:
            RA = ToDegrees(Math.Atan(0.91764 * Math.Tan(ToRadians(L))));

            while (RA < 0)
            {
                RAx = RA + 360;
                Debug.Assert(RAx != RA);
                RA = RAx;
            }

            while (RA >= 360)
            {
                RAx = RA - 360;
                Debug.Assert(RAx != RA);
                RA = RAx;
            }

            // right ascension value needs to be in the same quadrant as L:
            Lquadrant = Math.Floor(L / 90) * 90;
            RAquadrant = Math.Floor(RA / 90) * 90;
            RA = RA + (Lquadrant - RAquadrant);

            // right ascension value needs to be converted into hours:
            RA /= 15;

            // calculate the sun's declination:
            sinDec = 0.39782 * Math.Sin(ToRadians(L));
            cosDec = Math.Cos(Math.Asin(sinDec));

            // calculate the sun's local hour angle:
            cosH = (Math.Cos(ToRadians(zenith)) - (sinDec * Math.Sin(ToRadians(latitude)))) / (cosDec * Math.Cos(ToRadians(latitude)));

            // finish calculating H and convert into hours:
            if (getSunrise)
                H = 360 - ToDegrees(Math.Acos(cosH));
            else
                H = ToDegrees(Math.Acos(cosH));

            H = H / 15;

            // calculate local mean time:
            T = H + RA - (0.06571 * t) - 6.622;

            // convert to UTC:
            UT = T - lngHour;

            while (UT < 0)
            {
                UTx = UT + 24;
                Debug.Assert(UTx != UT);
                UT = UTx;
            }

            while (UT >= 24)
            {
                UTx = UT - 24;
                Debug.Assert(UTx != UT);
                UT = UTx;
            }

            return UT;
        }