private static DateTime SeasonAdjustedMorningTwilight(
double latitude, int day, int year, DateTime sunrise)
{
double a = 75 + ((28.65 / 55.0) * Math.Abs(latitude));
double b = 75 + ((19.44 / 55.0) * Math.Abs(latitude));
double c = 75 + ((32.74 / 55.0) * Math.Abs(latitude));
double d = 75 + ((48.10 / 55.0) * Math.Abs(latitude));
double adjustment;
int dyy = PrayerTimes.DaysSinceSolstice(day, year, latitude);
if (dyy < 91)
{
adjustment = a + (b - a) / 91.0 * dyy;
}
else if (dyy < 137)
{
adjustment = b + (c - b) / 46.0 * (dyy - 91);
}
else if (dyy < 183)
{
adjustment = c + (d - c) / 46.0 * (dyy - 137);
}
else if (dyy < 229)
{
adjustment = d + (c - d) / 46.0 * (dyy - 183);
}
else if (dyy < 275)
{
adjustment = c + (b - c) / 46.0 * (dyy - 229);
}
else
{
adjustment = b + (a - b) / 91.0 * (dyy - 275);
}
return(sunrise.AddSeconds(-(int)Math.Round(adjustment * 60.0)));
}
private static DateTime SeasonAdjustedEveningTwilight(
double latitude, int day, int year, DateTime sunset)
{
double a = 75 + ((25.60 / 55.0) * Math.Abs(latitude));
double b = 75 + ((2.050 / 55.0) * Math.Abs(latitude));
double c = 75 - ((9.210 / 55.0) * Math.Abs(latitude));
double d = 75 + ((6.140 / 55.0) * Math.Abs(latitude));
double adjustment;
int dyy = PrayerTimes.DaysSinceSolstice(day, year, latitude);
if (dyy < 91)
{
adjustment = a + (b - a) / 91.0 * dyy;
}
else if (dyy < 137)
{
adjustment = b + (c - b) / 46.0 * (dyy - 91);
}
else if (dyy < 183)
{
adjustment = c + (d - c) / 46.0 * (dyy - 137);
}
else if (dyy < 229)
{
adjustment = d + (c - d) / 46.0 * (dyy - 183);
}
else if (dyy < 275)
{
adjustment = c + (b - c) / 46.0 * (dyy - 229);
}
else
{
adjustment = b + (a - b) / 91.0 * (dyy - 275);
}
return(sunset.AddSeconds((int)Math.Round(adjustment * 60.0)));
}
private PrayerTimes(Coordinates coordinates, DateTime date, CalculationParameters parameters)
{
DateTime?tempFajr = null;
DateTime?tempSunrise = null;
DateTime?tempDhuhr = null;
DateTime?tempAsr = null;
DateTime?tempMaghrib = null;
DateTime?tempIsha = null;
//DateTime calendar = date.ToUniversalTime();
int year = date.Year;
int dayOfYear = date.DayOfYear;
SolarTime solarTime = new SolarTime(date, coordinates);
TimeComponents timeComponents = TimeComponents.FromDouble(solarTime.Transit);
DateTime? transit = timeComponents?.DateComponents(date);
timeComponents = TimeComponents.FromDouble(solarTime.Sunrise);
DateTime?sunriseComponents = timeComponents?.DateComponents(date);
timeComponents = TimeComponents.FromDouble(solarTime.Sunset);
DateTime?sunsetComponents = timeComponents?.DateComponents(date);
bool error = transit == null || sunriseComponents == null || sunsetComponents == null;
if (!error)
{
tempDhuhr = transit;
tempSunrise = sunriseComponents;
tempMaghrib = sunsetComponents;
timeComponents = TimeComponents.FromDouble(
solarTime.Afternoon(parameters.Madhab.GetShadowLength()));
if (timeComponents != null)
{
tempAsr = timeComponents.DateComponents(date);
}
// get night length
DateTime tomorrowSunrise = sunriseComponents.Value.AddDays(1);
double night = tomorrowSunrise.GetTime() - sunsetComponents.Value.GetTime();
timeComponents = TimeComponents
.FromDouble(solarTime.HourAngle(-parameters.FajrAngle, false));
if (timeComponents != null)
{
tempFajr = timeComponents.DateComponents(date);
}
if (parameters.Method == CalculationMethod.MOON_SIGHTING_COMMITTEE &&
coordinates.Latitude >= 55)
{
tempFajr = sunriseComponents.Value.AddSeconds(-1 * (int)(night / 7000));
}
NightPortions nightPortions = parameters.NightPortions();
DateTime safeFajr;
if (parameters.Method == CalculationMethod.MOON_SIGHTING_COMMITTEE)
{
safeFajr = SeasonAdjustedMorningTwilight(coordinates.Latitude, dayOfYear, year, sunriseComponents.Value);
}
else
{
double portion = nightPortions.Fajr;
long nightFraction = (long)(portion * night / 1000);
safeFajr = sunriseComponents.Value.AddSeconds(-1 * (int)nightFraction);
}
if (tempFajr == null || tempFajr.Value.Before(safeFajr))
{
tempFajr = safeFajr;
}
// Isha calculation with check against safe value
if (parameters.IshaInterval > 0)
{
tempIsha = tempMaghrib.Value.AddSeconds(parameters.IshaInterval * 60);
}
else
{
timeComponents = TimeComponents.FromDouble(
solarTime.HourAngle(-parameters.IshaAngle, true));
if (timeComponents != null)
{
tempIsha = timeComponents.DateComponents(date);
}
if (parameters.Method == CalculationMethod.MOON_SIGHTING_COMMITTEE &&
coordinates.Latitude >= 55)
{
long nightFraction = (long)night / 7000;
tempIsha = sunsetComponents.Value.AddSeconds(nightFraction);
}
DateTime safeIsha;
if (parameters.Method == CalculationMethod.MOON_SIGHTING_COMMITTEE)
{
safeIsha = PrayerTimes.SeasonAdjustedEveningTwilight(
coordinates.Latitude, dayOfYear, year, sunsetComponents.Value);
}
else
{
double portion = nightPortions.Isha;
long nightFraction = (long)(portion * night / 1000);
safeIsha = sunsetComponents.Value.AddSeconds(nightFraction);
}
if (tempIsha == null || (tempIsha.Value.After(safeIsha)))
{
tempIsha = safeIsha;
}
}
}
if (error || tempAsr == null)
{
// if we don't have all prayer times then initialization failed
this.Fajr = DateTime.MinValue;
this.Sunrise = DateTime.MinValue;
this.Dhuhr = DateTime.MinValue;
this.Asr = DateTime.MinValue;
this.Maghrib = DateTime.MinValue;
this.Isha = DateTime.MinValue;
}
else
{
// Assign final times to public struct members with all offsets
this.Fajr = CalendarUtil.RoundedMinute(tempFajr.Value.AddMinutes(parameters.Adjustments.Fajr + parameters.MethodAdjustments.Fajr));
this.Sunrise = CalendarUtil.RoundedMinute(tempSunrise.Value.AddMinutes(parameters.Adjustments.Sunrise + parameters.MethodAdjustments.Sunrise));
this.Dhuhr = CalendarUtil.RoundedMinute(tempDhuhr.Value.AddMinutes(parameters.Adjustments.Dhuhr + parameters.MethodAdjustments.Dhuhr));
this.Asr = CalendarUtil.RoundedMinute(tempAsr.Value.AddMinutes(parameters.Adjustments.Asr + parameters.MethodAdjustments.Asr));
this.Maghrib = CalendarUtil.RoundedMinute(tempMaghrib.Value.AddMinutes(parameters.Adjustments.Maghrib + parameters.MethodAdjustments.Maghrib));
this.Isha = CalendarUtil.RoundedMinute(tempIsha.Value.AddMinutes(parameters.Adjustments.Isha + parameters.MethodAdjustments.Isha));
}
}