From Friday at 8 a.m. to Monday at 4:30 p.m. I would work my standard 8 hour day on Friday, go on-call at the end of the day and through the weekend dealing with any and all emergencies our patient's might have, finishing my on-call hours when I went in for my typical 8 hour day on Monday. If the weekend was particularly rough, they would "try" to give you Monday off, but it didn't happen often.
It was pretty awful even though you could nap between visits. Some weekends were essentially non-stop running from one crisis to another. About two years ago, we changed that schedule to a half-weekend on-call shared between two nurses. It's soooo much better and we don't care that we have to work weekends more frequently (1 full weekend every 6 weeks vs. a half-weekend every 3 weeks) because the sleep and work-life balance is so much better.