Dallas is 14 hours behind Osaka
There is no standard 8-to-6 overlap. Someone joins early or late.
Practically speaking, Osaka and Dallas never share office hours; 14 hours of separation keeps their days apart. To talk live, someone has to flex: an early start in Dallas can catch the tail end of the day in Osaka, or the other way round. Bear in mind Dallas shifts for daylight saving while Osaka stays fixed — recheck these hours after each clock change.