The sky and the sun; light and open air. Often used in phrases regarding visibility or being trapped.

Justice or light; used figuratively to describe a state of lawfulness or liberation, as in the phrases 暗无天日 àn​wú​tiān​rì or 重见天日 chóng​jiàn​tiān​rì

(Mainland China) A period of time; days.

(Literary) The authority or laws of an emperor.