public LocalDate Add(LocalDate localDate, int value)
{
if (value == 0)
{
return(localDate);
}
int daysToAdd = value * unitDays;
var calendar = localDate.Calendar;
// If we know it will be in this year, next year, or the previous year...
if (daysToAdd < 300 && daysToAdd > -300)
{
YearMonthDayCalculator calculator = calendar.YearMonthDayCalculator;
YearMonthDay yearMonthDay = localDate.YearMonthDay;
int year = yearMonthDay.Year;
int month = yearMonthDay.Month;
int day = yearMonthDay.Day;
int newDayOfMonth = day + daysToAdd;
if (1 <= newDayOfMonth && newDayOfMonth <= calculator.GetDaysInMonth(year, month))
{
return(new LocalDate(new YearMonthDayCalendar(year, month, newDayOfMonth, calendar.Ordinal)));
}
int dayOfYear = calculator.GetDayOfYear(yearMonthDay);
int newDayOfYear = dayOfYear + daysToAdd;
if (newDayOfYear < 1)
{
newDayOfYear += calculator.GetDaysInYear(year - 1);
year--;
if (year < calculator.MinYear)
{
throw new OverflowException("Date computation would underflow the minimum year of the calendar");
}
}
else
{
int daysInYear = calculator.GetDaysInYear(year);
if (newDayOfYear > daysInYear)
{
newDayOfYear -= daysInYear;
year++;
if (year > calculator.MaxYear)
{
throw new OverflowException("Date computation would overflow the maximum year of the calendar");
}
}
}
return(new LocalDate(calculator.GetYearMonthDay(year, newDayOfYear).WithCalendarOrdinal(calendar.Ordinal)));
}
// LocalDate constructor will validate.
int days = localDate.DaysSinceEpoch + daysToAdd;
return(new LocalDate(days, calendar));
}
