[O] Point jumps when changing timestamps

[Matt Lundin]

I often change timestamps  with S-Left or S-Right when the cursor is at
the point immediately following the timestamp:

<2011-08-03 Wed .+1d>
                     ^ cursor here

When I call S-Left or S-Right at this point, the cursor jumps to the
last character of the day of week abbreviation:

<2011-08-04 Thu .+1d>
              ^ cursor now here

The cursor does not jump if it is already located within the brackets.

Best,
Matt