4. The time difference between Sydney and Beijing is 3 hours, for example: when it is 12:00 in Sydney, it is 9:00 in Beijing. On a certain day, when it is 9:15 in Sydney, Xiao Ma and Xiao Yang depart from Sydney and Beijing respectively to go to the other's location. Xiao Ma arrives in Beijing at 19:33 Beijing time. The ratio of the travel time for Xiao Ma and Xiao Yang is 7:6. What is the local time in Sydney when Xiao Yang arrives? $\qquad$ —.
20:39