Dhaka is 10 hours ahead of Washington, D.C.

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

The 10-hour offset between Washington, D.C. and Dhaka means there's no point hunting for a 9-to-5 overlap — there isn't one. Expect compromise: someone in Washington, D.C. or Dhaka will need to take the call outside the usual 9-to-5, so share that load. Remember that Washington, D.C. shifts for daylight saving and Dhaka doesn't, so recalculate the overlap after each clock change.