Ottawa is 10.5 hours behind Colombo
There is no standard 8-to-6 overlap. Someone joins early or late.
Ottawa is 10.5 hours behind Colombo, which is far enough that a normal 9-to-5 in one city never reaches the other's working hours. One practical option: Ottawa dials in early while it's still late afternoon or evening in Colombo. Remember that Ottawa shifts for daylight saving and Colombo doesn't, so recalculate the overlap after each clock change.