Vancouver is 2 hours behind Ottawa
Best overlap: 10:00 AM to 6:00 PM in Ottawa is 8:00 AM to 4:00 PM in Vancouver.
Shoot for 10:00 AM to 6:00 PM in Ottawa; your Vancouver colleagues will see that as 8:00 AM to 4:00 PM. The overlap is wide at 8 hours, so you can protect mornings for deep work and still find plenty of meeting time.