[Calc] Date field updated only at creation

Dear all,

In one of my template, I have a field which is the creation date of the document.

So when I create a new document based on this template, I would like this date to be updated.
But then when I edit this saved document later, I would like this date not to change anymore.

At the moment I just added a Validity option on my cell with this formula : TEXT(TODAY();“YYMMDD”)
So each time I create a new document I have to clic on this cell and choose the current date from the dropdown menu.

Is there any better way to do this?

Thank you for your assistance!

Florian