Beijing is 1.5 hours behind Adelaide
Best overlap: 9:30 AM to 6:30 PM in Adelaide is 8:00 AM to 5:00 PM in Beijing.
Shoot for 9:30 AM to 6:30 PM in Adelaide; your Beijing colleagues will see that as 8:00 AM to 5:00 PM. That's a roomy 9 hours of common time each day, so finding a slot that suits everyone is rarely a problem. For part of the year the maths changes: Adelaide observes daylight saving, Beijing does not, shifting the overlap by an hour.