Melbourne is 16 hours ahead of Ottawa
Best overlap: 4:00 PM to 6:00 PM in Ottawa is 8:00 AM to 10:00 AM in Melbourne.
Target 4:00 PM to 6:00 PM in Ottawa, which lands at 8:00 AM to 10:00 AM for the Melbourne side. The overlap barely stretches to 2 hours, so reserve it for what really needs a live conversation and handle the rest async. The date rolls over between them: Melbourne is on the next day relative to Ottawa during these hours.