Do I need the transit visa if I don't leave the airport

I'll travel Calgary-Vancouver-Shanghai-Bangkok and then after 2 weeks back to Canada: Bangkok-Kunming-Nanjing-Vancouver-Calgary. It looks like I won't leave the Airbus between Kunming-Nanjing-Vancouver because it's just a stop in Nanjing. Do I need the 72-hour free transit if I won't leave any of the airports and the total duration at the airport doesn't exceed 24 hours? I'm Canadian citizen.