One of the most famous wars between the gods and the Asuras (demons) is the Tarakamaya war. The war was started when Chandra the moon god kidnapped Tara, wife of Brihaspati guru of the gods. (Brihaspati is often just called Guru, and he's the god of the planet Jupiter.). To rescue their guru's wife, the gods fought a great war against Chandra, and the Asuras took Chandra's side since he was opposing the gods. In the end Chandra gave back Tara, but not before she became pregnant with his son, Budha god of the planet Mercury.

In any case, the army of the gods was led by Shiva, who fought on Brihaspati's side because of his loyaly to Brihaspati's father Angiras, as described in the Vishnu Purana:

In vain Vrihaspati sought to recover his bride; in vain Brahmá commanded, and the holy sages remonstrated; Soma [Chandra] refused to relinquish her. Uśanas [Sukracharya], out of enmity to Vrihaspati, took part with Soma. Rudra [Shiva], who had studied under Angiras, the father of Vrihaspati, befriended his fellow-student. In consequence of Uśanas, their preceptor, joining Soma, Jambha, Kujambha, and all the Daityas, Dánavas, and other foes of the gods, came also to his assistance; whilst Indra and all the gods were the allies of Vrihaspati.
My question is, what is the story of Shiva studying under the sage Angiras?

Now Angiras was one of the mind-born sons of Brahma, so he's certainly old enough. But are there any other scriptures that describe Shiva as a student of Angiras? Are there any other details known about this?