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wkstart --주시작하는 기준요일


public int Weeks(int year, int month, DayOfWeek wkstart)
{

DateTime first = new DateTime(year, month, 1);
int firstwkday = (int)first.DayOfWeek;

int otherwkday = (int)wkstart;
int offset = ((otherwkday + 7) - firstwkday) % 7;

double weeks = (double)(DateTime.DaysInMonth(year, month) - offset) / 7d; return (int)Math.Ceiling(weeks);
}