/* Returns the addition of two durations.
*/
public static SchemaDuration durationAdd(SchemaDuration duration1, SchemaDuration duration2) {
SchemaDuration dur = new SchemaDuration();
dur.setNegative(false); // sets isempty to false
int ym = duration1.getYearMonthValue() + duration2.getYearMonthValue();
long dt = duration1.getDayTimeValue() + duration2.getDayTimeValue();
if ((ym < 0 && dt > 0) || (ym > 0 && dt < 0))
throw new NotANumberException(
"Invalid duration result, yearmonth part differs in sign from daytime part.");
if (ym != 0) dur.setYearMonthValue(ym);
if (dt != 0) dur.setDayTimeValue(dt);
return dur;
}
