I actually liked the one time zone system in China when I lived there. It made scheduling work across different cities a little more convenient, and I didn't mind that the sunrise/sunset didn't always exactly line up to what I am accustomed to.
But it would definitely screw up cultural references, e.g.: a "5pm tea" then can only be understood with a broader cultural context: "UK, 5pm is late in the 2nd half of the working day for them".