I've seen various contracting positions offering daily rates (IT industry). I'm guessing that if you are only there for a short time and they are paying per day, then they'd try to get as many hours out of you as they can?
I know that this would vary between employers and the only way to get a good answer is to talk to who is offering the job, but it'd be useful to have a rough guide of what to expect just so that I can convert between hourly and daily rates when browsing job ads and considering which positions I want to apply to.
NB. If anyone is worried about subjectivity, then it is possible to answer this question with a survey of what hours contractors tend to work on average, ect.