Depends on the university. Some ask for weeks, some ask for hours, some ask for days, some just ask for dates.
Off the top of my head RVC asked for days, Edinburgh asked for hours, Liverpool asked for weeks and Bristol asked for days but that was a year ago so I can't promise that's correct. Can't comment for any other universities either.
In general one week = five working days and one day = eight hours so you can guesstimate from there (be honest though, and make sure your employers/supervisors agree with the figures that you're putting down as they can chase it up).