What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
You may like to add "Dates Difference" widget in form which will calculate and save the number of dates between two dates.
Alternatively you can add two date fields in your form and then calculate the difference by adding formula in "Form Calculation" widget. Please check the screenshot below:
Please take a look at the following demo form I created for you: https://form.jotform.com/70736379711967
Feel free to clone this form for a closer look. The following guide should help you in form cloning: https://www.jotform.com/help/42-How-to-Clone-an-Existing-Form-from-a-URL
Hope this helps.
Do get back to us if you have any questions.