Glynn Clements wrote:

Bayley, Alistair wrote:

You also need to specify, or let the user specify, the order of
arithmetic.  I.e. adding a day and then a second is different from
doing it the other way around.


Only when leap seconds are involved. A month and a day would be a
better example.

Duration arithmetic is not commutative? Can you give some examples please,
because I'm not able to imagine any.


	April 30th + 1 month + 1 day = May 30th + 1 day = May 31st
	April 30th + 1 day + 1 month = May 1st + 1 month = June 1st

What reason is there to say May 30 + 1 day == May 31st? May 30 + 1 day = June first. So the answer is the same either way, as long as your result for May 30 + 1 day is correct.