Warsaw is 6 hours ahead of Washington, D.C.
Best overlap: 8:00 AM to 12:00 PM in Washington, D.C. is 2:00 PM to 6:00 PM in Warsaw.
Keep meetings inside 8:00 AM to 12:00 PM in Washington, D.C. — that maps to 2:00 PM to 6:00 PM in Warsaw. Around 4 hours of overlap is enough to work comfortably, as long as meetings don't drift to the end of one team's day.