To Americans, punctuality is a way of showing respect for other people's time. Being more than 10 minutes late to an appointment usually calls for an apology, and maybe an explanation. People who are running late often call ahead to let others know of the delay. Of course, the less formal the situation, the less important it is to be exactly on time. At informal get-togethers, for example, people often arrive as much as 30 minutes past the appointed time. But they usually don't try that at work.