Automatic Current Date without changing later.

I am using Adobe Acrobat 9.0 Standard.  (I know, it's old.)

I have a date field and I would like it to automatically enter the current date as the user is completing the form, but then, if the form is saved and then opened on a different day, I would like it to display the original date, no longer the current date.

I guess, what I'm asking for is for Acrobat to get the current date, place it in the field, them make it a "static" date that will not change later.

Please help,

Thaks, John