/// <summary>
/// get the next jieqi on or after a specific date
/// </summary>
/// <param name="startDate">start date on Beijing Time</param>
/// <returns></returns>
public static CJieqi GetNextJieqi(DateTime startDate)
{
double d0 = DateTimeUtil.DateTimeToJulian(startDate.AddHours(-1 * BEJING_TIME_ZONE));
double longitude0 = Earth.EclipticLongitude(d0);
int nextJieqi = (int)Math.Floor(longitude0 / 15) + 1;
int nextDegree = nextJieqi * 15;
DateTime nextJieqiTime = Earth.GetEclipticLongitudeTime(startDate, nextDegree);
return(new CJieqi(nextJieqi % 24, nextJieqiTime.AddHours(BEJING_TIME_ZONE)));
}
/// <summary>
/// Calculate Chinese New Year, see http://www.math.nus.edu.sg/aslaksen/calendar/chinese.shtml
/// </summary>
/// <param name="year"></param>
/// <returns></returns>
public static DateTime GetChineseNewYear(int year)
{
//first give the December solstice time
DateTime temp0 = new DateTime(year - 1, 12, 15);
DateTime temp1 = Earth.GetEclipticLongitudeTime(temp0, 90);
DateTime sui0 = GetBeijingTime(temp1); //this is the begig of sui
temp0 = new DateTime(year, 12, 15);
temp1 = Earth.GetEclipticLongitudeTime(temp0, 90);
DateTime sui1 = GetBeijingTime(temp1); //this is the begin of next sui
ArrayList monthes = new ArrayList(); //hold the start of each months during this sui
//apply the rule #4, find the number of new Moon in a sui
temp0 = MoonPhases.TruePhase(sui0, MPhase.New); //next new Moon time
temp0 = GetBeijingTime(temp0);
monthes.Add(temp0);
int newYearMonth = 1; //for normal year, New Year would be the second monthes
if (temp0 == sui0) //new moon at the same date as begining of sui, it is 11 month
{
newYearMonth = 2;
}
while (temp0 < sui1)
{
temp1 = MoonPhases.TruePhase(temp0.AddDays(28), MPhase.New); //next new Moon time
temp1 = GetBeijingTime(temp1);
if (temp1 < sui1)
{
monthes.Add(temp1);
temp0 = temp1;
}
else
{
break;
}
}
if (monthes.Count == 13 && newYearMonth == 1) //leap sui
{
//apply rule #5, see if the month 11 or 12th is leap month;
temp0 = Earth.GetEclipticLongitudeTime((DateTime)monthes[0], 105);
temp0 = GetBeijingTime(temp0);
if (temp0 > (DateTime)monthes[1]) //first monthes is leap month
{
newYearMonth = 2;
}
else
{
//apply rule #5, see if the month 11 or 12th is leap month;
temp0 = Earth.GetEclipticLongitudeTime((DateTime)monthes[1], 120);
temp0 = GetBeijingTime(temp0);
if (temp0 > (DateTime)monthes[2]) //second monthes is leap month
{
newYearMonth = 2;
}
}
}
return((DateTime)monthes[newYearMonth]);
}