How can I see if form responses have been edited after submission?

I have a form set up to allow edits from users after they submit responses, and would like to be able to capture when any edits take place. In other words, if a form is reopened by the submitter to change responses, is it possible to set up a fixed/pre-populated field (date or otherwise) to know when the responses were edited? Is it already recorded elsewhere?

Though there is a submission data by default, this is not updated when the submission is edited, a good  way to achieve it could be adding a date field and set it to hidden, here are the steps. 

1. Add the field to your form and set the default date as the current date. 

2. Once the step above is done, you will need to click on the gear icon and click on the option hide field as shown on the image below. 

You will capture the date each time  that the form is submitted, for example, when the form is submitted this value will be the same as the submission date, but if the form is re-opened and the user submits the form again then this date will be updated and you will know that this was update and the exact date when it happened.

Hope this will help you.