Find duration between 2 fields with data type (Time of day) ?

Do you mean the start date and end date should be same day? My use case is something like this:

Start date can be 1st dec and end date can be 5th dec. Also I need to know the time of start day and end day so I can display a result. For example: "Outage Duratio" was 4 days and 7 hours. Can this be achieved?

Yes no problem, but let me know what you are fields are which are capturing the start date and end date.  i suggest that you make fields for those and btw, a user tip is that if you type a T into a date field it will populate to today.

So you may want to default the start date to the current day and then users will type a T to set the date when the ticket is closed, as well as the time.  or else you can have a form rule to check a checkbox that will set the  end date to today and the end time to now.

Thank you for your help, I tweaked my field types and was able to find the solution in "Days Format".