Holi is the day of coloured powder and water, of music and sweets, and of a brief social levelling in which age and rank are set aside. It follows the night of Holika Dahan, when a bonfire is lit to recall the burning of the demoness Holika and the deliverance of the child devotee Prahlada.
Holika Dahan takes place on the full-moon night (Purnima) of the month of Phalguna, and the play of colour follows on the next morning, the first tithi of the waning fortnight. The time of the bonfire is fixed to the pradosh period after sunset, avoiding the inauspicious bhadra interval, so it varies by location.
Observance differs by region: the Braj area around Mathura and Vrindavan keeps an extended week of celebration, parts of the south treat the day more quietly as a rite for Kamadeva, and in some eastern traditions it coincides with Dol Purnima and processions of Krishna and Radha.