Helsinki is 7 hours ahead of Ottawa
Best overlap: 8:00 AM to 11:00 AM in Ottawa is 3:00 PM to 6:00 PM in Helsinki.
For a call that suits both sides, look at 8:00 AM to 11:00 AM in Ottawa / 3:00 PM to 6:00 PM in Helsinki. You share roughly 3 hours a day. That's enough for regular meetings, but treat the window as prime time and guard it.