When is Onam?ओणम कब है?

Hindu date: Thiruvonam nakshatra in the Malayalam month of Chingam (solar Simha).

Onam is the day Thiruvonam (Shravana) nakshatra is current at sunrise in Chingam.

Dates are calculated for New Delhi; elsewhere they can fall a day earlier or later. Month names follow the Purnimanta calendar used in North India, where a month ends on Purnima. How we calculate

King Mahabali ruled Kerala so justly that the gods grew anxious. Vishnu came as Vamana and asked for three paces of land, covering earth and heaven in two and placing the third on Mahabali's head, sending him to the netherworld, but granting him a yearly visit to his people. Onam is that homecoming.

Celebrations run for ten days from Atham to Thiruvonam, with a fresh pookalam each day, new clothes (onakkodi), the Onasadya feast on a banana leaf, vallam kali boat races and Pulikali dances.