I am not exactly sure what this means but since I have translated 通 as "comprehend" elsewhere, I do the same here. In 2.06, the way "comprehends thing as one"; here the true people comprehend the seasons as four. I trust the idea is that their joy and anger are timely, but exactly how you get that, I am not sure. Compare the description of Confucius as the sage of timeliness in Mencius 5 B 10.