Why is Diwali on Amavasya?

Everyone knows Diwali falls on Amavasya. Almost nobody asks why.

Why not Purnima? The full moon is the brightest night of the month. A festival of lights on a full-moon night would have been easier, prettier, better lit. The tradition had the option and did not take it.

Amavasya is the night the moon is not there. It sits between the earth and the sun with its lit face turned away, and for one night there is nothing in the sky to see by.

It is a tithi, not a date. It begins and ends at calculated moments that have nothing to do with midnight, so it can start late one morning and end late the next, and the civil date it belongs to depends on which part of which day it covers. This is why Diwali moves in the calendar, and why your family’s panchang can put it on a different date from someone else’s.

And in the rest of the year, Amavasya is when the departed are remembered. Be it tarpan, shraddh or the rites that face backwards. Twelve of them a year, and that is what they are for.

The Padma Purana gives Deepavali its own chapter. In the Uttara Khanda, Chapter 122, Shiva is answering Kartikeya, who has asked what the festival is for and which deity it belongs to.

What the chapter prescribes, within a single stretch of verses, is this.

In the morning, after the bath: worship of the deities and of the ancestors, the parvana shraddh offered with curd, ghee and milk, brahmanas fed. And at nightfall: lamps offered to Yama outside the house, lamps offered to Naraka, and then lamps placed at the temples of Brahma, Vishnu and Shiva, and at rooftops, assembly halls, rivers, ramparts, gardens, wells, streets and stables.

Lakshmi, the chapter says, resides in the oil, and should be awakened through the women of the house.

Where are these lamps lit? Rivers, ramparts, wells, streets, stables. These are not altars. They are the parts of a settlement that have no light in them at night, and the chapter sends lamps to every one.

So the answer to the question is in the structure of the chapter rather than in any one sentence of it. On this one amavasya, the tradition does both things at once: it keeps the day for the departed in the morning, and then it lights every dark place it can name. Not instead of the ancestors.

The Skanda Purana covers the same festival across its Kartika chapters, and carries the Yama lamp, the Naraka Chaturdashi bath, the worship of Bali and the sister’s meal. Between the two texts, the four days around this one are all accounted for.

Three things follow from this that are worth knowing.

1.     Lakshmi Puja is a pradosh-kaal observance, so what matters is whether amavasya is current after sunset. It is entirely normal for amavasya to continue into the following morning and for that following day not to be Diwali at all, because by evening it has ended.

2.     The lamps belong in the dark places. If you are deciding where to put them and the chapter is your guide, the altar is not the priority - the doorway, the stairwell, the terrace, the gate, the part of the lane outside your house that nobody lights. That is what the list in the text is describing, and it is a different instinct from arranging them where they will look best.

3.     If your household does shraddh or tarpan on amavasya, this one is not an exception and the two are not in competition. The morning rite and the evening lamps are the same day’s observance.

Once you see it, the same logic is all over Kartik. The whole month is a deepdaan month - lamps given through the dark half, not only on the one night. The Yama lamp at Dhanteras is lit outside the house, away from the shrine. And at the far end of the month, Kartik Purnima turns it inside out: Dev Deepawali puts lamps on water under a full moon, where they are not needed for light at all and are purely an offering.

It also explains why Amavasya being the day for the departed is not a conflict to resolve. A lamp set down in a dark place for someone who is not there to see it is the same gesture as a lamp set at a well. Both are given rather than used.