/// <summary>
/// Calculate 24 solar terms.
/// </summary>
/// <param name="year">Year.</param>
/// <param name="term">Solar term.</param>
/// <param name="localTimeZone">Local time zone.</param>
/// <returns>The <see cref="DateTime"/> of solar term.</returns>
/// <remarks>
/// If you want to calculate the equinox and solstice, please use the method <see cref="GetEquinoxAndSolstice"/>.
/// </remarks>
public DateTime GetSolarTerms(int year, SolarTerm term, TimeZoneInfo localTimeZone)
{
// Estimate iteration start time interval
EstimateSTtimeScope(year, term, out double lJD, out double rJD);
double solarTermsJD = 0.0;
double longitude = 0.0;
DateTime solarTermsTime = new DateTime();
do
{
solarTermsJD = ((rJD - lJD) * 0.618) + lJD;
solarTermsTime = Julian.ToCalendarDay(solarTermsJD);
longitude = CoordinateSystem.Equator2Ecliptic(GetEquatorCoordinate(solarTermsTime, true), solarTermsTime, true).Longitude;
// In the iterative approximation of 0 degree of ecliptic longitude, the estimated value of ecliptic longitude may be in the interval of (345,360] and [0,15) due to the 360 degree circularity of the angle. If the value falls into the previous interval, it needs to be corrected.
longitude = ((term == 0) && (longitude > 345.0)) ? longitude - 360.0 : longitude;
if (longitude > (int)term)
{
rJD = solarTermsJD;
}
else
{
lJD = solarTermsJD;
}
} while ((rJD - lJD) > 0.0001);
// Min +2 correction
return(TimeZoneInfo.ConvertTime(solarTermsTime.AddMinutes(2), TimeZoneInfo.Utc, localTimeZone));
}
internal void EstimateSTtimeScope(int year, SolarTerm term, out double lJD, out double rJD)
{
switch (term)
{
case SolarTerm.BeginningOfSpring:
lJD = Julian.ToJulianDay(new DateTime(year, 2, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 2, 9));
break;
case SolarTerm.RainWater:
lJD = Julian.ToJulianDay(new DateTime(year, 2, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 2, 24));
break;
case SolarTerm.WakingOfInsects:
lJD = Julian.ToJulianDay(new DateTime(year, 3, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 3, 9));
break;
case SolarTerm.SpringEquinox:
lJD = Julian.ToJulianDay(new DateTime(year, 3, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 3, 24));
break;
case SolarTerm.PureBrightness:
lJD = Julian.ToJulianDay(new DateTime(year, 4, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 4, 9));
break;
case SolarTerm.GrainRain:
lJD = Julian.ToJulianDay(new DateTime(year, 4, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 4, 24));
break;
case SolarTerm.BeginningOfSummer:
lJD = Julian.ToJulianDay(new DateTime(year, 5, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 5, 9));
break;
case SolarTerm.LesserFullness:
lJD = Julian.ToJulianDay(new DateTime(year, 5, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 5, 24));
break;
case SolarTerm.GrainInEar:
lJD = Julian.ToJulianDay(new DateTime(year, 6, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 6, 9));
break;
case SolarTerm.SummerSolstice:
lJD = Julian.ToJulianDay(new DateTime(year, 6, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 6, 24));
break;
case SolarTerm.LesserHeat:
lJD = Julian.ToJulianDay(new DateTime(year, 7, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 7, 9));
break;
case SolarTerm.GreaterHeat:
lJD = Julian.ToJulianDay(new DateTime(year, 7, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 7, 24));
break;
case SolarTerm.BeginningOfAutumn:
lJD = Julian.ToJulianDay(new DateTime(year, 8, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 8, 9));
break;
case SolarTerm.EndOfHeat:
lJD = Julian.ToJulianDay(new DateTime(year, 8, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 8, 24));
break;
case SolarTerm.WhiteDew:
lJD = Julian.ToJulianDay(new DateTime(year, 9, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 9, 9));
break;
case SolarTerm.AutumnalEquinox:
lJD = Julian.ToJulianDay(new DateTime(year, 9, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 9, 24));
break;
case SolarTerm.ColdDew:
lJD = Julian.ToJulianDay(new DateTime(year, 10, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 10, 9));
break;
case SolarTerm.FirstFrost:
lJD = Julian.ToJulianDay(new DateTime(year, 10, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 10, 24));
break;
case SolarTerm.BeginningOfWinter:
lJD = Julian.ToJulianDay(new DateTime(year, 11, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 11, 9));
break;
case SolarTerm.LesserSnow:
lJD = Julian.ToJulianDay(new DateTime(year, 11, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 11, 24));
break;
case SolarTerm.GreaterSnow:
lJD = Julian.ToJulianDay(new DateTime(year, 12, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 12, 9));
break;
case SolarTerm.WinterSolstice:
lJD = Julian.ToJulianDay(new DateTime(year, 12, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 12, 24));
break;
case SolarTerm.LesserCold:
lJD = Julian.ToJulianDay(new DateTime(year, 1, 4));
rJD = Julian.ToJulianDay(new DateTime(year, 1, 9));
break;
case SolarTerm.GreaterCold:
lJD = Julian.ToJulianDay(new DateTime(year, 1, 16));
rJD = Julian.ToJulianDay(new DateTime(year, 1, 24));
break;
default:
lJD = 0;
rJD = 0;
break;
}
}
/// <summary> /// Elément de syntax pour définir une date solaire. /// </summary> /// <param name="value">Terme solaire.</param> /// <returns>L'élément de syntax <see cref="Composition.SolarDate"/> pour ajouter d'autres comportements.</returns> public SolarDate SolarDate(SolarTerm value) => new SolarDate(this, value);
/// <summary> /// Initialise une nouvelle instance de la classe <see cref="LunarDate"/>. /// </summary> /// <param name="parent">Elément de syntax parent.</param> /// <param name="value">Terme solaire.</param> public SolarDate(ExpressionElement parent, SolarTerm value) : base(parent) => Value = value;
