Ottawa is 7 hours behind Athens
Best overlap: 3:00 PM to 6:00 PM in Athens is 8:00 AM to 11:00 AM in Ottawa.
Shoot for 3:00 PM to 6:00 PM in Athens; your Ottawa colleagues will see that as 8:00 AM to 11:00 AM. Since Ottawa is 7 hours behind Athens, the workdays overlap by around 3 hours; 3:00 PM in Athens (8:00 AM in Ottawa) makes a reliable recurring slot.