/// <summary>
/// Initializes a new instance of the <see cref="DaylightHours"/> class.
/// </summary>
/// <param name="location">
/// The location.
/// </param>
/// <param name="day">
/// The day.
/// </param>
/// <param name="sunrise">
/// The sunrise time.
/// </param>
/// <param name="sunset">
/// The sunset time.
/// </param>
private DaylightHours(GeographicLocation location, DateTimeOffset day, TimeSpan?sunrise, TimeSpan?sunset)
{
_day = day;
_location = location;
_sunrise = sunrise;
_sunset = sunset;
}
private static DaylightHours CalculateCore(DateTimeOffset day, GeographicLocation location)
{
double jdate = ToJulian(day);
double n = Math.Round((jdate - BaseJulianDays - 0.0009D) - (location.LongitudeWest / 360D));
double jnoon = BaseJulianDays + 0.0009D + (location.LongitudeWest / 360D) + n;
double m = (EarthDegreesPerYear + (EarthDegreesPerDay * (jnoon - BaseJulianDays))) % 360;
double c = (EarthEocCoeff1 * Sin(m)) + (EarthEocCoeff2 * Sin(2 * m)) + (EarthEocCoeff3 * Sin(3 * m));
double sunLon = (m + EarthPerihelion + c + 180D) % 360;
double jtransit = jnoon + (EarthTransitJ1 * Sin(m)) + (EarthTransitJ2 * Sin(2 * sunLon));
int iteration = 0;
double oldMean;
do
{
oldMean = m;
m = (EarthDegreesPerYear + (EarthDegreesPerDay * (jtransit - BaseJulianDays))) % 360;
c = (EarthEocCoeff1 * Sin(m)) + (EarthEocCoeff2 * Sin(2 * m)) + (EarthEocCoeff3 * Sin(3 * m));
sunLon = (m + EarthPerihelion + c + 180D) % 360;
jtransit = jnoon + (EarthTransitJ1 * Sin(m)) + (EarthTransitJ2 * Sin(2 * sunLon));
}while (iteration++ < 100 && Math.Abs(m - oldMean) > Epsilon);
double sunDec = Asin(Sin(sunLon) * Sin(EarthObliquity));
double h = Acos((Sin(EarthSolarDiskDiameter) - Sin(location.Latitude) * Sin(sunDec)) / (Cos(location.Latitude) * Cos(sunDec)));
if (Math.Abs(h) < Epsilon || double.IsNaN(h) || double.IsInfinity(h))
{
return(new DaylightHours(location, day, null, null));
}
double jnoon2 = BaseJulianDays + 0.0009D + ((h + location.LongitudeWest) / 360D) + n;
double jset = jnoon2 + (EarthTransitJ1 * Sin(m)) + (EarthTransitJ2 * Sin(2 * sunLon));
double jrise = jtransit - (jset - jtransit);
DateTimeOffset sunrise = FromJulian(jrise);
Debug.Assert(sunrise.Date == day.Date, "Wrong sunrise", "Sunrise: Expected {0:D} but got {1:D} instead.", day, sunrise.Date);
DateTimeOffset sunset = FromJulian(jset);
Debug.Assert(sunset.Date == day.Date, "Wrong sunset", "Sunset: Expected {0:D} but got {1:D} instead.", day, sunset.Date);
return(new DaylightHours(location, day, sunrise.TimeOfDay, sunset.TimeOfDay));
}
/// <summary>
/// Calculates the sunrise and sunset days for the specified date and location.
/// </summary>
/// <param name="year">
/// The year for which the times are calculated.
/// </param>
/// <param name="month">
/// The month for which the times are calculated.
/// </param>
/// <param name="day">
/// The day for which the times are calculated.
/// </param>
/// <param name="location">
/// The <see cref="GeographicLocation"/> for which the times are calculated.
/// </param>
/// <returns>
/// A <see cref="DaylightHours"/> instance representing the calculated times.
/// This value will never be <see langword="null"/>, although the sunrise/sunset times could be.
/// </returns>
/// <exception cref="ArgumentOutOfRangeException">
/// <para><paramref name="year"/> is less than 1 or greater than 9999.</para>
/// <para>-or-</para>
/// <para><paramref name="month"/> is less than 1 or greater than 12.</para>
/// <para>-or-</para>
/// <para><paramref name="day"/> is less than 1 or greater than the number of days in the specified month.</para>
/// <para>-or-</para>
/// <para>The specified date is earlier than <see cref="DateTimeOffset.MinValue"/> or later than <see cref="DateTimeOffset.MaxValue"/>.</para>
/// </exception>
/// <exception cref="InvalidOperationException">
/// There was an error with the calculation.
/// </exception>
public static DaylightHours Calculate(int year, int month, int day, GeographicLocation location)
{
var date = new DateTimeOffset(year, month, day, 0, 0, 0, TimeSpan.Zero);
return(CalculateCore(date, location));
}
/// <summary>
/// Calculates the sunrise and sunset days for the specified date and location.
/// </summary>
/// <param name="day">
/// The date for which the times are calculated.
/// </param>
/// <param name="location">
/// The <see cref="GeographicLocation"/> for which the times are calculated.
/// </param>
/// <returns>
/// A <see cref="DaylightHours"/> instance representing the calculated times.
/// This value will never be <see langword="null"/>, although the sunrise/sunset times could be.
/// </returns>
/// <exception cref="InvalidOperationException">
/// There was an error with the calculation.
/// </exception>
public static DaylightHours Calculate(DateTime day, GeographicLocation location)
{
return(CalculateCore(day.ToUniversalTime().Date, location));
}
/// <summary>
/// Calculates the sunrise and sunset days for the specified date and location.
/// </summary>
/// <param name="day">
/// The date for which the times are calculated.
/// </param>
/// <param name="location">
/// The <see cref="GeographicLocation"/> for which the times are calculated.
/// </param>
/// <returns>
/// A <see cref="DaylightHours"/> instance representing the calculated times.
/// This value will never be <see langword="null"/>, although the sunrise/sunset times could be.
/// </returns>
/// <exception cref="InvalidOperationException">
/// There was an error with the calculation.
/// </exception>
public static DaylightHours Calculate(DateTimeOffset day, GeographicLocation location)
{
return(CalculateCore(day.UtcDateTime.Date, location));
}