The rest of India celebrates this day (or sometimes the day after) as Diwali, the festival of lights and the largest and most popular festival of India as a whole.
Bengalis have coincided this with the puja of Kali. Kali epitomizes the darker and more aggressive form of the mother goddess. Kali Puja is Bengal's own festival given the fact that one of the most well known Kali temples in the world is located at Kalighat, from where Kolkata (Kalighat -> Kalighata -> Kolikata -> Kolkata) derives its name.
Kali Puja is also performed as community puja. Puja committees who have a smaller budget or perhaps want to distinguish themselves from the many others who are organizing Durga Puja, organize Kali Puja with pomp and splendour.
Since Kali Puja also coincides with Diwali, Bengalis celebrate Kali Puja with burning of crackers. There used to be a custom (and now becoming extinct) where a day before the kali Puja, all the local trash was collated and heaped and then burnt ("nyarapora" or "burning the bald" ) - probably an ancient means to clean the environment.
Enjoy the festival of lights and the puja of the goddess of darkness!
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