Date arithmetic in tables

["Chris Randle" <chris@amlog.co.uk>]

Hi All

This post started as a problem and question, but I found a solution. I
thought I'd document my observations. Forgive me if it's obvious, but it
wasn't to me!

I had trouble with date arithmetic in an org table, I think because the
function thought that inactive dates were vectors:

| Date             | Days before today
|
|------------------+----------------------------------------------------
----|
| <2008-03-22 Sat> | 38.540
|
| [2008-03-22 Sat] | [<2002-11-24 Sun 12:57>, <2008-04-29 Tue 12:57> -
Sat] |
#+TBLFM: $2=now()-$1

I didn't want to use active dates, as I didn't want the heading to
appear in the agenda. Starting to play around, I discovered that

<[2008-03-22 Sat]>

would work as an inactive date acceptable to the formula, but the
trailing ">" was stripped when using keystrokes to adjust the date. So
then I noticed that

<[2008-03-22 Sat]

would work still, and nothing was lost during adjustment. Which finally
led to the discovery that

[2008-03-22 Sat]

also works if the formula is adjusted to

#+TBLFM: $2=now()-<$1>

Hope this helps others.

-- 
Chris Randle
Org-mode 6.02. Emacs 22.1.1. Windows XP.