Houston is 12 hours behind Hanoi

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

The 12-hour difference means Hanoi and Houston miss each other entirely during regular office hours. Where you can, lean on async updates and save live calls for when one team is happy to start early or stay late. Daylight saving complicates things slightly: Houston observes it, Hanoi doesn't, so the difference flexes by an hour part of the year.