Denver is 11.5 hours behind Colombo

There is no standard 8-to-6 overlap. Someone joins early or late.

Denver is 11.5 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: Denver dials in early while it's still late afternoon or evening in Colombo. Finally, Denver observes daylight saving and Colombo doesn't, so this window shifts by an hour for part of the year — recheck it each spring and autumn.