Flight Guangzhou Baiyun International Airport departs from Guangzhou Guangzhou Baiyun International Airport at 01:15 and arrives at Seoul Incheon International Airport at 05:45.
The flighttime is about 3h 30m. The distance travelled ("as the bird flies"): 1648 Km. So the average speed is roughly 471 Km.
There is an 1 hour time difference between Guangzhou and Seoul