public static int GetSolarTermIndex(DateTime date) => Sun.GetSolarTermIndex(date.AddHours(-ILocalInfoProvider.GetLocalInfoProvider <T>().TimeZone).AddHours(24));
public static string GetDayTerrestrialBranchName(int solarYear, int solarMonth, int solarDay) => ILocalInfoProvider.GetLocalInfoProvider <T>().BranchNames[GetDayTerrestrialIndex(solarYear, solarMonth, solarDay)];
///// <summary>
///// 0 -> 12, 1 -> 1, 2 -> 2, 3 -> 3... 11 -> 11
///// </summary>
///// <param name="monthIndex"></param>
///// <returns></returns>
//public static int GetMonth(int monthIndex) { return monthIndex == 0 ? 12 : monthIndex; }
#endregion
#region Day
public static string GetSolarTermName(DateTime date)
{
return(ILocalInfoProvider.GetLocalInfoProvider <T>().SolarTerms[GetSolarTermIndex(date)]);
}
public static string GetDayCelestialStemName(int solarYear, int solarMonth, int solarDay) => ILocalInfoProvider.GetLocalInfoProvider <T>().StemNames[GetDayCelestialStemIndex(solarYear, solarMonth, solarDay)];
internal static LuniSolarDate <T> CalculateLuniSolarDateFromSolarDate(int year, int month, int day)
{
// Sample case 1: Solar date 24/05/2000 --- Lunar date 21/04/2000
// previousNewMoon = 04/05/2000
// lunarYear = previousNewMoon.Year = 2000
// newMoon11Before = 08/12/1999
// newMoon11After = 26/11/2000
// (04/05/2000 - 08/12/1999) / 29 = 148 days / 29
// = 5.10x
// --------------------------------------------------------------
// Sample case 2: Solar date 01/01/2014 --- Lunar date 01/12/2013
// previousNewMoon = 01/01/2014
// previousNewMoon.Year = 2014
// lunarYear = 2013
// newMoon11Before = 03/12/2013
// newMoon11After = 26/11/2000
// (01/01/2014 - 03/12/2013) / 29 = 29 days / 29
// = 1
// --------------------------------------------------------------
// Sample case 3: Solar date 22/12/2033 --- Lunar date 01/11i/2033
// previousNewMoon = 22/12/2033
// lunarYear = previousNewMoon.Year = 2033
// newMoon11Before = 03/12/2032
// newMoon11After = 22/11/2033
var timeZone = ILocalInfoProvider.GetLocalInfoProvider <T>().TimeZone;
int lunarYear;
int lunarMonth;
int lunarDay;
bool isLeapMonth = false;
var thisDay = new DateTime(year, month, day);
var k = (int)((thisDay.AddHours(-timeZone).UniversalDateTimeToJulianDate() - 2415021.076998695) / Constants.SynodicMonth + 0.5);
var previousNewMoon =
JulianDateConverter.JulianDateToUniversalDateTime(Moon.GetNewMoon(k)).AddHours(timeZone).Date;
while (previousNewMoon > thisDay)
{
previousNewMoon =
JulianDateConverter.JulianDateToUniversalDateTime(Moon.GetNewMoon(--k)).AddHours(timeZone).Date;
}
// "previous, this/current" and "next" are not used to avoid ambiguity.
var newMoon11Before = Moon.GetNewMoon11(previousNewMoon.Year - 1, timeZone).Date;
var newMoon11After = Moon.GetNewMoon11(previousNewMoon.Year, timeZone).Date;
// correcting for such cases as case 3
if (newMoon11After < previousNewMoon)
{
newMoon11Before = newMoon11After;
newMoon11After = Moon.GetNewMoon11(previousNewMoon.Year + 1, timeZone).Date;
}
var isLeapYear = (newMoon11After - newMoon11Before).TotalDays > 365.0;
var monthsFromNewMoon11Before = (int)((previousNewMoon - newMoon11Before).TotalDays / 29);
/* Note:
* monthsFromNewMoon11Before = 0: lunar month = 11, lunar year = previous year
* monthsFromNewMoon11Before = 1: lunar month = 12, lunar year = previous year
* monthsFromNewMoon11Before = 2: lunar month = 1, lunar year = this year
* monthsFromNewMoon11Before = 3: lunar month = 2, lunar year = this year
* and so on
*/
// month 11 and 12 belong to lunar year of the previous year.
if (monthsFromNewMoon11Before < 2)
{
lunarYear = newMoon11After.Year - 1;
lunarMonth = 11 + monthsFromNewMoon11Before;
}
else
{
lunarYear = newMoon11After.Year;
lunarMonth = monthsFromNewMoon11Before - 1;
}
// correcting month number if this lunar year is leap year
if (isLeapYear)
{
var leapMonthIndex = LuniSolarCalendar <VietnameseLocalInfoProvider> .GetLunarYear(newMoon11After.Year).LeapMonthIndex;
if (monthsFromNewMoon11Before >= leapMonthIndex)
{
lunarMonth--;
if (monthsFromNewMoon11Before == leapMonthIndex)
{
isLeapMonth = true;
}
}
}
lunarDay = (int)(thisDay - previousNewMoon).TotalDays + 1;
return(new LuniSolarDate <T>(lunarYear, lunarMonth, isLeapMonth, lunarDay, thisDay));
}