Seconds wont convert over from string using format function

I have a table with dates in DateTime format:

When I try to break them down to s string using Format, the time always comes back as "12:00:00 AM"

Heres the DAX I am using:

Harvest Hours = Format(DATEVALUE( MAX('Abattoir RecordScan'[EventDate])),"MM/dd/yyyy hh:mm:ss AM/PM")

Ultimately, I am trying to get the MAX and MIN datetime from a day and then Subtract to get the total time between the two.

Is my DAX wrong? 

Am I going about this all wrong?

Any help appreciated