Ottawa is 7 hours behind Helsinki
Best overlap: 3:00 PM to 6:00 PM in Helsinki is 8:00 AM to 11:00 AM in Ottawa.
For the smoothest call, aim inside 3:00 PM to 6:00 PM in Helsinki, i.e. 8:00 AM to 11:00 AM in Ottawa. Since Ottawa is 7 hours behind Helsinki, the workdays overlap by around 3 hours; 3:00 PM in Helsinki (8:00 AM in Ottawa) makes a reliable recurring slot.