Date and Time Calculation

My order form has a list of services (Example: Hourly Parking). I have a Check-in Date/Time field on the form and I would like to provide a calculated field that displays till what date/time the reservation is valid through.

Example: 

Check-in Date/Time: 06/20/2020 11:00

and customer selected in the product section 2.5 hours, then the form would calculate and show till what date/time the parking is valid.

i.e. Valid Through 06/20/2020 13:30

Is there a way to do that?

Unfortunately, it is not possible to calculate time based on a payment field.

I suggest you list your products using regular fields, then assign calculation values.

How-to-Assign-Calculation-Value

Once done, you can calculate the validity using Form Calculation widget.

How-to-Perform-Form-Calculation-Using-a-Widget

The guide below should help you with generating time related formula:

Mastering-Date-and-Time-Calculation

You should also have another Form Calculation widget that will calculate the price, then pass that price to your payment field:

How-to-Pass-a-Calculation-to-a-Payment-Field