[O] Active timestamp drawer with inactive creation-date

[Alexander Poslavsky]

Hi!

I actively use timestamps to plan my day. When I have a task, I add a 
time-stamp to it with "C-." Then I plan the task, for example, for tomorrow. I 
end up with:

** important task <2013-03-13 Wed>
   :PROPERTIES:
   :CREATED:  <2013-03-12 Tue 13:52>
   :END:

The property drawer has an active time-stamp, which in turn appears in my 
agenda. What I want to end up is, an inactive time-stamp in the drawer:

** important task <2013-03-13 Wed>
   :PROPERTIES:
   :CREATED:  [2013-03-12 Tue 13:52]
   :END:

At the moment I change it by hand, but laziness is the key to progress, so: how 
do I do this?

Thanks, Alex