out = plus (obj, B) ¶Addition: add to a calendarDuration.
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.
B may be a calendarDuration, duration, or numeric.
If B is numeric, it is converted to a calendarDuration
using caldays(B).
Returns a calendarDuration.