“Thus the Sabbath begins in [the eastern border of] China eighteen hours later than it does in the Land of Israel. For the Land of Israel is situated in the center of the inhabited world.”
If that’s true, then I’ve been doing it 24 hours early for as long as I’ve been in China. I am assuming that there has been a p’sak issued to the contrary, having us work from commonly accepted time.
Either way, Shabbat Shalom!