Nothing, that'll teach me not to read the whole doc
Spoiler:
Cool, but why merge the value and type into 1 element?
Wouldn't it be easier to separate them into 2 like
date_arithmetic(date, value, type, fmt*)
is much more understandable, right?
EDIT: crap, I thought that as the function was not yet officially implemented, I thought we had time to "debate" it.
But the question remains.