Ayudha Puja is observed on ninth day of Shukla Paksha (waxing phase of moon) in Ashwin month. In Tamil Nadu, Ayuda Pooja is in Puratasi month and in Kerala it is in the Kanni month. Ayudha Puja 2015 date is October 21. In Kerala it is on October 21 and 22. Literally, Ayudha Puja means the worship of weapons. On the day books, tools and objects used for making a living is worshipped and ritual purification is performed.
The books and objects that are kept for ritual purification are only taken on the next day morning after pujas and rituals. The day is also the last day of Saraswati Puja. In
South India, therefore the day is also known as Shastra Puja.
Legend has it that the weapons used by Goddess Durga were worshipped on the day. The day is known as Astra Puja in
Bengal and is observed on Durga Ashtami day.
You can find more details of Ayudha Puja in this earlier article.