Are work experience hours counted by standard workday or is it more specific?

37.5hrs is the standard workday, so is it enough to approximate to the nearest week and say I worked here for 100 weeks thus that's 3750 hours? How granular do you have to be? I'm trying to figure out when I should be applying for the charter. One of my jobs is also definitely not a 9-5, so do I get extra for that or are we still only taking the standard weekday? I assume not.