They call 8 PM on Friday "working late"? Where I work, we call 4:30 PM on Friday working late. We have flexible hours. My contracted hours are 37 a week. At the end of each 4 week period I can be up to 14 hours in credit or debit. The office is open 7:30 AM to 6:45 PM. Core time (when you must be there) is 10 AM to 12 noon, and 2 PM to 3:30 PM. If I get to work at 7:30 AM and take half an hour for lunch I can go home at 3:30 PM and still make up time, at the rate of 6 minutes per day. Our PCs have a thing called "Night Watchman" that logs you off at 7 PM, but site security would turf you out at 6:45 PM anyhow. When I have 7 hours 24 minutes surplus time, I can have a day off. Or "borrow" that time, thus not touching my annual leave allowance.