I am making a driver to calculate various holidays in a given time span. So, I need to find the Gregorian dates of all the Chinese Holidays (Chinese New Year, QingMing Festival, Dragon Boat Festival, etc). I used the famous 'Easter algorithm' for Good Friday, Easter Monday, Ascension Day, and Whit Monday calculations; however, I don't understand it well enough to adapt it for the Chinese calendar.
I have found similar questions, but they often go from Gregorian to Chinese:
Calculating lunar/lunisolar holidays in python
http://www.herongyang.com/year/program.html
http://www.hermetic.ch/cal_stud/ch_year.htm
The last link was exremely helpful but I'm still not sure how to implement that algorithm in a way that can help me. Any advice or code would be greatly appreciated!
Here is my Good Friday Algorithm:
private void GetGoodFridayOccurances(DateTime startDate, DateTime endDate, List<ObservedHoliday> observedHolidays, StandardHoliday holiday)
{
for (DateTime date = startDate; date <= endDate; date = date.AddYears(1))
{
#region Finding the Day of Easter Algorithm
int day, month;
int firstTwo = date.Year / 100;
int remainderMod = date.Year % 19;
int pfmDate = (firstTwo - 15) / 2 + 202 - 11 * remainderMod;
#region switches
switch (firstTwo)
{
case 21:
case 24:
case 25:
case 27:
case 28:
case 29:
case 30:
case 31:
case 32:
case 34:
case 35:
case 38:
pfmDate = pfmDate - 1;
break;
case 33:
case 36:
case 37:
case 39:
case 40:
pfmDate = pfmDate - 2;
break;
}
#endregion
pfmDate = pfmDate % 30;
int tA = pfmDate + 21;
if (pfmDate == 29)
tA = tA - 1;
if (pfmDate == 29 && remainderMod > 10)
tA = tA - 1;
//Find next sunday
int tB = (tA - 19) % 7;
int tC = (40 - firstTwo) % 4;
if (tC == 3 || tC > 1)
tC = tC + 1;
pfmDate = date.Year % 100;
int tD = (pfmDate + pfmDate / 4) % 7;
int tE = ((20 - tB - tC - tD) % 7) + 1;
day = tA + tE;
if (day > 31)
{
day = day - 31;
month = 4;
}
else
{
month = 3;
}
#endregion
DateTime observed = new DateTime(date.Year, month, day).AddDays(-2);
ObservedHoliday obsdate = new ObservedHoliday(holiday);
if (startDate == endDate && startDate.Day == observed.Day)
{
obsdate.DateObserved = observed;
observedHolidays.Add(obsdate);
}
else if (startDate != endDate && observed >= startDate)
{
obsdate.DateObserved = observed;
observedHolidays.Add(obsdate);
}
}
For Chinese New Year, I think this would work:
.NET 6 Support:
Now that .NET 6 (finally) has the
DateOnly
type (after we've been asking for it for 20 years now...), this works:(Unfortunately .NET 6's
Calendar
class hasn't yet been updated to supportDateOnly
, but it's straightforward to handle manually):So running this...
...gives me this output: