Hong Kong and Shenzhen are in the same time zone. Both cities use UTC+8. When it's noon in Hong Kong, it's also noon in Shenzhen.
Neither city observes daylight saving time.
Any time works! Since both cities are in the same time zone, scheduling is never an issue.
Hong Kong and Shenzhen are neighboring cities separated by the border. High-speed trains connect them in about 15 minutes.