I now do this calculation myself every time before arriving. 180 days from Friday March 7 = September 3. So expect your stamp to say either 2 Sept or 3 Sept. A difference of one or two days isn't a big deal so I wouldn't fuss over it. Plus, they may have a different way of counting that 180.
Forget this stupid lawyer idea. It WON'T work! Embassies have the right to reject with or without a reason. Just go to Vietnam and apply under soft power category. Far much easier and cheaper. Lots of people are getting approved that way.