My departure time from Amsterdam for Guanghzhou, China will be 13:30 on the 4th. September. My visa stipulates that I must enter China before the 5th. Will there be a problem because of the time difference going east?
Although the visa says "enter before", according to the Chinese Embassy in the USA, the visa is
good through 24h00 Beijing Time of the "Enter Before" date unless the number of entries is used up or the visa is revoked by the Chinese government.
If you're flying direct, your flight should arrive around 7h00 on the 5th, Beijing time.
Airline tickets and itineraries almost always give local times for all stops, so if yours says you're landing at 7h00, that refers to Beijing time.