How do I put a field that will stamp the date of form submission?

How do I put a field that will stamp the date of form submission? 

On the submissions page of your form, there's already a submissions date column.

Example:

If you want to add that on email notification, simply use {DATE} field variable.

Guide: https://www.jotform.com/help/68-Add-a-Date-on-Email-Notification