There are a lot of factors for a county jail. Looking at the possibility of intakes. At a jail you get a lot of intakes (admissions) from arrests, etc. Depending on what the activity is in your area, the evening and night is pretty active. Day time you will deal with routine stuff like a clinic. Find out more details on that part. If it is a settled state prison (like they have gone to court already and serving their sentence) it is on a more regular schedule.