Well, looking at it another way, there's probably a distribution of times of day when people start working, including as late as 10:00 or 11:00 am. So, assuming

Well, looking at it another way, there's probably a distribution of times of day when people start working, including as late as 10:00 or 11:00 am. So, assuming that this anecdotal experience is representative (and it might well not be), it is surprising that no-one is in the office at 7:30 or 8:00 pm. Either the entrainment effect of the culture is so strong that everyone comes in at 8:00 in the morning, or folks are coming in late and leaving early.