Holi is a two-day spring festival, also known as the festival of colours, which starts on Purnima (Full Moon day) falling in the Hindu Calendar month of Phalgun (somewhere between the end of February and Mid-March, in the Gregorian Calendar).
This ancient festival is mentioned in the Puranas, and by the poet Kalidasa during the 4th century reign of Chandragupta II; the celebration of Holi is also mentioned in the 7th-century Sanskrit drama Ratnavali and in Dashakumaracharita, as well. It is also believed that Krishna played Holi with the gopis (milkmaids)
Celebrations vary from region to region, but, in general, on the evening of the first day (Holika Dahan), people gather around a bonfire.
Holika was the evil sister of the demon king Hiranyakashipu. According to legends, he was the King of Multan and had earned a boon that made him indestructible. He grew arrogant, thought he was God, and demanded that everyone worship only him.
Hiranyakashipu’s own son, Prahlada disagreed. He was and remained devoted to Lord Vishnu, which infuriated Hiranyakashipu. He subjected Prahlada to cruel punishments, none of which affected the boy. Finally, Holika - Prahlada’s aunt - tricked him into sitting on a pyre with her. Holika was wearing a cloak that made her immune to injury from fire, while Prahlada was not. As the fire roared, the cloak flew from Holika and encased Prahlada. Holika burned, Prahlada survived. Seeing this, Hiranyakashipu, unable to control his anger, smashed a pillar with his mace. There was a tumultuous sound, and Lord Vishnu appeared as Lord Narasimha and killed Hiranyakashipu. The next day, when the fire cooled down, people applied ash to their foreheads, a practice still observed by some people. Eventually, coloured powder came to be used to celebrate Holi.
The bonfire is a reminder of the symbolic victory of good over evil, of Prahlada over Hiranyakashipu, and of the fire that burned Holika.
The second day of Holi represents a festive ocassion when people celebrate, play with colors, sing and dance. Everybody is welcomed to participate, irrespective of age, status or caste; it is a joyful opportunity to have fun, celebrate spring, celebrate the good that prevails over evil, a moment to forgive and forget, to repair broken relationships.