Before Deepavali what was it?

Deepavali is a "recent" festival..that is only after the advent of the Avatars of Lord Vishnu.

The North celebrates it becos of Lord Rama going back to Ayodhya and the South celebrates is becos of Krishna/Sathyabama Vs Narakasura ordeal.

Whatever the reason Deepavali is a Vaishnava celebration.

So what was the major celebration in India for all Hindu prior to Rama or Krishna?

Any idea?

BTW what about hardcore Shaivites? How do they view Deepavali?

Isn't there a Shaiva equivalent to a Deepavali?