Riyadh is 8 hours ahead of Ottawa
Best overlap: 8:00 AM to 10:00 AM in Ottawa is 4:00 PM to 6:00 PM in Riyadh.
Target 8:00 AM to 10:00 AM in Ottawa, which lands at 4:00 PM to 6:00 PM for the Riyadh side. The overlap barely stretches to 2 hours, so reserve it for what really needs a live conversation and handle the rest async. Note that Ottawa follows daylight saving while Riyadh stays put, so the times above drift by an hour seasonally.