Dave Rolsky wrote:
This means that if you do subtract_datetime on two objects you end up with this situation:

  $dur = $dt2 - $dt1
  $dt1 + $dur != $dt2
  $dt2 - $dur != $dt1

So, assuming America/Chicago: (2003-12-01) - (2003-09-01) will return a duration representing 2 months, 29 days and 23 hours?

If so, I'd prefer it returned a duration object representing n seconds ...

THEN I'd like to see another 'local difference' function that worked down from years ..
2003 - 2003 = 0 years
  12 -   09 = 3 months
  01 -   01 = 0 days

(extending .. (2004-01-23) - (2003-09-01) becomes:

2004 - 2003 =  1 year   \    auto normalises    /  0 years
  01 -   09 = -8 months  >--  to get rid of  --<   4 months
  23 -   01 = 22 days   /    negative values    \ 22 days

)

Then again, I wonder if durations shouldn't be removed altogether and put into separate packages that allowed people to choose their math assumptions.

Cheers!
Rick Measham

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