Uhh, actually there IS only one time-zone for China, UTC+08:00.

Granted they USED to have 5 (or more?) timezones and their geographic size suggests that they should, but China has standardized the whole country on Beijing time.  The result is that on the west side of the country sunrise and sunset happen very late.  At the winter solstice sunrise doesn't happen until about 10:30am in some areas while sunset is around 7:30pm.

South Korea is all on UTC+09:00, so one hour off of China.

North Korea, just to be different, is at UTC+08:30.