Karachi is 3 hours ahead of Bucharest
Best overlap: 8:00 AM to 3:00 PM in Bucharest is 11:00 AM to 6:00 PM in Karachi.
8:00 AM to 3:00 PM in Bucharest is when Karachi is also working, at 11:00 AM to 6:00 PM their time. With 7 hours in common, treat scheduling almost as if the two cities were in the same region. Watch the DST gap — when Bucharest changes its clocks and Karachi stays the same, this window slides by an hour.