Best overlap: 1:00 PM to 6:00 PM in Karachi is 8:00 AM to 1:00 PM in Edinburgh.
Book within 1:00 PM to 6:00 PM Karachi time (8:00 AM to 1:00 PM in Edinburgh) and both teams will be at work. A 5-hour overlap gives you a workable daily window; aim for earlier in it to avoid clipping the end of someone's day. Don't be caught out by clock changes — Edinburgh observes daylight saving and Karachi doesn't, so the offset varies by an hour through the year.
London to New York is five hours apart, except for the five weeks a year when it isn't. Exact overlap windows for every US zone, the 2026 DST mismatch dates, and where to put the recurring sync. -