Portland is 11 hours behind Moscow
There is no standard 8-to-6 overlap. Someone joins early or late.
Practically speaking, Moscow and Portland never share office hours; 11 hours of separation keeps their days apart. To talk live, someone has to flex: an early start in Portland can catch the tail end of the day in Moscow, or the other way round. Note the seasonal wrinkle: when Portland is on daylight saving and Moscow isn't, the gap between them grows or shrinks by an hour.