We're discussing an amount of time.

I wasn't discussing anything, I was asking a question.

so 2007-11-07 plus one year is 2008-11-07.

Thanks. That's 366 days, so DM actually handles years properly.

I don't have an answer for months, but I'm going to assume they're handle properly (Jan 1st + 1 month = Feb 1st).

I don't have a crystal clear answer for days, but it sounds like days aren't handled properly — It's possible to add a day without a date change or add a day and have the date change by two days — and it's slated to be fixed.

It could be interesting to study the differences between DT and DM wrt the corner cases, but it's not what I was asking, and any interest and time I might have had has waned.