How to update a timestamp?

[Alain.Cochard@unistra.fr]

Hello.

The manual says that 

"When point is at an existing timestamp in the buffer, ['C-c .'
(‘org-time-stamp’)] is used to modify this timestamp instead of
inserting a new one."

but the default value is the existing date, not the current one so it
is not convenient at all for me.

In fact, I am looking for the equivalents of 'C-u C-u C-c .' and 'C-u
C-u C-c !' but without the time -- just the date.

I couldn't find it in the manual nor after searching the Internet.
If this does not exist, I am making it a feature request.

Thanks in advance.