Kali Puja is kept on the dark new Moon night of autumn, the same night that most of India celebrates Diwali with Lakshmi puja. In Bengal, Odisha, Assam and Tripura, however, it is the goddess Kali who is worshipped, and the main puja is held after midnight. The night is called Dipanwita Amavasya in Bengal, the new moon of lamps, and the streets and homes are filled with lamps, candles and fireworks.
Month and tithi
The festival is the Amavasya of Ashwina in the amanta calendar, which north India counts as Kartika. It is the same new moon night as Diwali; see Diwali. The tithi is the thirtieth, described on the Amavasya page.
Who is Kali
Kali is the fierce form of the goddess, black, wearing a garland of skulls and standing on Shiva. The tradition reads her as the power that destroys fear and ignorance, and her worshippers see her as a mother. The Devi Mahatmya and the Tantras speak of her, and the poet-saint Ramprasad Sen of eighteenth century Bengal wrote songs to her that are still sung. Images of Kali for the puja are made of clay and set up in homes, in local clubs and in the temples of Kolkata, including Dakshineswar and Kalighat.
How it is kept
The goddess is worshipped at night with red hibiscus flowers, rice, lentils, fruit, sweets and incense, and in some traditions with an offering of fish or other food that the family customarily gives. In Bengali homes, a lamp for each ancestor is lit the evening before, on Bhoot Chaturdashi, when fourteen lamps are lit and fourteen kinds of leafy greens are eaten. The main puja is performed after midnight, often lasting for an hour or more. Cracker fireworks follow, and the festival ends with the immersion of the clay image the next day or soon after.
How the date and time are fixed
The rule used here follows Drik Panchang: the festival is the civil day on which Amavasya is in force at Nishita, the short window around the middle of the night. If Amavasya covers that moment on two nights, the first is taken. The window in the table is the Nishita Kaal itself, so the puja time runs from just before midnight until some time after, and it is the moment the worship traditionally begins.
Diwali’s Lakshmi puja is fixed by a different test, Amavasya in the evening after sunset (Pradosh). Because the two tests ask about different times of night, the Kali Puja can fall on the same civil day as Diwali or, in some years and cities, a day apart. The Diwali page gives the Lakshmi puja date and the Kali Chaudas page is the night before.
Why cities differ
The new moon is one instant for the whole world, but midnight is at a different time in every city, so the night on which Amavasya is in force at midnight can differ by a day between two cities. The table lists each city, and the any-city tool works out other places.
A calm note
If you take part in a late-night puja, plan your way home and keep to the safety rules for fireworks and for lamps near cloth. If your family or your local committee gives a time or day of its own, follow it.