Best overlap: 2:00 PM to 6:00 PM in Colombo is 8:30 AM to 12:30 PM in Edinburgh.
For the smoothest call, aim inside 2:00 PM to 6:00 PM in Colombo, i.e. 8:30 AM to 12:30 PM in Edinburgh. Edinburgh is 5.5 hours behind Colombo, so you've got a workable 4-hour overlap — ideal for a standing meeting around 2:00 PM in Colombo (8:30 AM in Edinburgh). Seasonal note: Edinburgh uses daylight saving and Colombo doesn't, so double-check the times in your own months — they can move by an hour.
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. -