What the epics say - 'Akalbodhan'

The worship of Devi Durga in the month of Ashwin is called 'Akalbodhan'- an uncustomary time for commencement of the worship. It is so called since the period of this worship differs from the conventional period (during the spring - 'Basanta'). Ramayana says that when Rama was engaged in the fierce battle with Ravana, he wanted to secure the blessings of victory from Devi Durga. He held the puja to evoke the goddess during autumn to his dire plight, thereby worshiping Durga untimely (in Akal). Hence this puja is called Akalbodhon.

It was customary to worship Durga with 100 neel kamals (blue lotuses). Rama could gather only 99 of them; he offered one of his eyes as a substitute of the 100th lotus. Pleased with his devotion Durga blessed him. The battle started on Shaptami and Ravana was killed at the Shandhikshan (in between) Ashtami and Navami; he was cremated on Dashami. Therefore the four days of the puja that we celebrate ends in the triumph of the good over evil.