Li Bai was a poet in the prosperous Tang Dynasty. At that time, the national strength was strong, and the literati were very keen on utilitarianism, eager to make contributions, ambitious and confident.
Bai Juyi was a poet in the middle Tang Dynasty, and his national strength was declining. Scholars hope to change the dark social reality and have the desire to revive the Tang Dynasty, but after their efforts, they find that everything is irreversible.
Du Fu, a poet in the prosperous Tang Dynasty, lived a rough life, was loyal to the monarch and loved the people, and reflected the thought of worrying about the country and the people in his immediate creation.
Li Bai and Du Fu both met and sang with each other. Therefore, Du Fu was by no means from the late Tang Dynasty.