Dussehra is also known as Vijaya Dasami, because of the victory of Ram over Ravana. On the day of Dussehra, Ram, killed the great demon Ravan, who had abducted Ram’s wife Sita to his kingdom of Lanka. Ram, along with his brother Lakshman and devoted follower Hanuman, and an army of monkeys fought a great battle to rescue his lovely wife Sita.
The war against Ravan lasted for ten days.
Sita had been returned to her husband Ram and they now make their way to Ayodhya in triumph and glory. Thus, it is on the Diwali day that Lord Ram, the incarnation of Lord Vishnu in the Treta Yug, returned to his capital Ayodhya after the exile of fourteen years.
Diwali comes exactly 20 days after Dussehra on Amavas (new moon), during fortnight of kartik, some time in October or November.