Chengdu Research Base of Giant Panda Breeding

Visiting the Giant Panda Breeding Base would not take more than 3 hrs. So you have more than sufficient time with your 12 hrs transit even if you are caught in the traffic, assuming you are coming in at 7am and departing at 7pm. You did not mention how you are getting in.If you are worried about the traffic,you can take the metro from the airport or railways to the Chengdu Zoo station on Line 3 and then take a taxi to the breeding base. The whole journey would not take you more than an hour.