How to create a dynamic custom stamp

Hi. - I'm not very technical so thanks in advance for any help you can give.

I want to be able to stamp, date and sign certain pdf's i receive and I've worked out how to create a custom stamp and use "fill and sign" for my signature but I need the stamp to be dynamic and show the date on which it is stamped. I can't work out how to do the last bit so please help.