In West Bengal the day of Maha Navami Puja varies from that of other states of India. It usually happens one day after the Mahanavami in other states.
In most of the Indian states, except Bengal, Mahanavami is observed based on Purva-Viddha rule. Purva-Viddha rule insists that if Navami Tithi prevails for 3 Muhurata before sunset on the previous day, then Mahanavami Puja and fasting should be observed on the previous day. If it happens, then both the Ashtami and Navami Puja including fasting are performed on the same day. However, it may be noted that this rule is applicable to Navami Puja and Navami fasting only, but not applicable to Navami Balidan. Various religious texts including Dharmasindhu and Nirnayasindhu have mentioned this rule.
In West Bengal, Para-Viddha rule is followed for observing Maha Navami. Para-Viddha rule insists that Mahanavami should be observed when it prevails at least for one Muhurata after Sunrise.
Further, in West Bengal, Mahanavami is the third and final day of Durga Puja and the Durga Puja on this day begins with Mahasnan and Shodashopachar Puja.
On Maha Navami, Goddess Durga is worshipped in the form of Mahisasuramardini, which means the Destroyer of the Buffalo Demon. It was on Maha Navami day Goddess Durga killed the demon Mahishasura.
Maha Navami Rituals:
# On this day, Goddess Durga is worshipped as Saraswati—the deity of knowledge and wisdom. In Southern India, Ayudha Puja is arranged and along with the Goddess, tools, machineries, musical instruments, books, equipments of all kinds including automobiles are decorated and worshipped. This day is considered vital before starting any new work on Vijaya Dashami.
# Children start going to school on this day in many places in Southern India.
# In North and East India, Kanya Pujan is done on this day in many places. According to this ritual, nine young virgin girls are worshipped as nine forms of Goddess Durga. Their feet are washed, kumkum and sandalwood paste is applied over them; they are offered new clothes to wear and then they are worshipped with mantras and incense sticks. Special food is cooked for them and they are offered gifts as tokens of love and respect by the devotees.
# In eastern India, Maha Navami is the third day of Durga Puja. This starts with a holy bath following which Shodhasopachar puja is done. On this day Devi Durga is worshipped as Mahishasuramardini, meaning the Goddess who killed Mahishasur, the buffalo demon. It is believed that on this day the demon was finally annihilated.
# A special ritual of Navami hom is done at the end of Navami puja.
# It is also believed that puja done on this day is equivalent to puja done on all the nine days of the Navratri festival.
# In some places, ancient tradition of Navami bali or sacrifice of animals is still practiced.
# In some areas of Andhra Pradesh, Batthukamma festival is held on Navami. The name is inspired by a beautiful flower. # # This puja is done by Hindu women and flowers are arranged in a typical seven layer form in a conical shape and is offered to Goddess Gauri—a form of Durga. This festival celebrates the glory and beauty of womanhood. Women wear new clothes and jewellery on this day.
# Other pujas that are held on this day are Suvasini Puja and Dampati puja.
# In Mysore, on this day the Royal sword is worshipped and is taken out in processions on illustrated elephants and camels.