You can use the
“Date & Time” (In)
“Date & Time” (Out)
Input > Date & Time (Out) - Date & Time (In) :format as minutes.
See image below, there is a plugin i think, you can use, so you dont need the dates.
There are prob other ways to achieve this, but this is how I do it.
ok i solved this by creating an Air Time Picker ( End Time ) & Air Time Picker ( Current Time ) then add an Input Field as the Result Time initial content will be End Time - Current Time :format as minutes then add a workflow to refresh page every minutes so that Current Time picker will show the latest current time