8.2.2.3 calendarDuration.plus

Method: out = plus (A, B)

Addition: add two calendarDurations.

All the calendar elements (properties) of the two inputs are added together. No normalization is done across the elements, aside from the normalization of NaNs.

If B is numeric, it is converted to a calendarDuration using calendarDuration.ofDays.

Returns a calendarDuration.