Bucharest is 5 hours behind Hanoi
Best overlap: 1:00 PM to 6:00 PM in Hanoi is 8:00 AM to 1:00 PM in Bucharest.
The hours that work for both Hanoi and Bucharest are 1:00 PM to 6:00 PM (Hanoi) and 8:00 AM to 1:00 PM (Bucharest). The shared window is roughly 5 hours; treat its midpoint as the default and you'll keep both teams happy. The difference isn't constant year-round: Bucharest adjusts for daylight saving while Hanoi holds steady.