Hey Nick, the first one came through just fine. This is pretty cool but
still not quite what I'm looking for.  It totally helped me get what I
wanted though!  I wanted to have a separate row for each day so I could fill
in activities.  Modifying your example I get:

| date             | place   | activity                  | notes
 |
|------------------+---------+---------------------------+------------------|
| <2010-03-19 Fri> |         |                           | dummy
 |
| <2010-03-20 Sat> |         |                           |
 |
| <2010-03-21 Sun> | moon    | collect rocks             |
 |
| <2010-03-22 Mon> | jupiter | thrash around the red dot |
 |
| <2010-03-23 Tue> | mars    | see the little green men  |
 |
| <2010-03-24 Wed> | earth   |                           | home, sweet home
|
#+TBLFM: @2$1 = <03-19-2010>::$1 = @-1$1 + 1

Exactly what I wanted!  I can insert days, move them around, and just hit
C-u C-c C-c to have it update.  I'd like to understand how it works though,
if you don't mind.  What does the ::$1 synax mean?  And how did it know that
we were dealing with a date?

On Wed, Mar 17, 2010 at 12:58 PM, Nick Dokos <nicholas.dokos@hp.com> wrote:

> Josh Mattoon <joshmattoon@gmail.com> wrote:
>
> > If I wanted to add an extra day on mars I could just enter a new row,
> recalculate the forumula, and
> > the dates would be automagically updated. It's not such a big deal in a
> small example like this but
> > I'm planning out a 3 week vacation with a fair number of destinations.
> I'd like the day of week to
> > display because some sites are closed on certain days.
>
> [Not sure what mailer mangled my previous reply to the point of
> unrecognizability, but here is another attempt - I hope it's
> cleaner. Let me know if there is a problem.]
>
>
> | date             | duration | place   | activity                  | notes
>            |
>
> |------------------+----------+---------+---------------------------+------------------|
> | <2010-03-17 Wed> |        0 |         |                           | dummy
>            |
> | <2010-03-17 Wed> |        3 | moon    | collect rocks             |
>            |
> | <2010-03-20 Sat> |        5 | mars    | see the little green men  |
>            |
> | <2010-03-25 Thu> |        5 | jupiter | thrash around the red dot |
>            |
> | <2010-03-30 Tue> |          | earth   |                           | home,
> sweet home |
> #+TBLFM: @2$1 = <03-17-2010>::$1 = @-1$1 + @-1$2
>