Holi – Festival of Colours, love & Friendship

​When Celebrated –
It is celebrated on full moon day in Hindi month called Phalgun (February March).

Why Celebrated - Significance

1. The festival usher onset of spring (Vasant Ritu) when flowers of various colour are in full bloom.
2. People visit family, friends and foes to throw coloured powders on each other; laugh and gossip, then share Holi delicacies, food and drink.
3. On Holi day, people forget their differences and re-unite.
4. In Bihar & UP, it marks the beginning of new year.
5. The festival symbolises victory of good over evil and restore faith in dharma.

How & Where Celebrated

1. Holi is celebrated on two days. Previous day of Holi is called "chhoti Holi" or Holika Dahan.
2. As a mark of Holika dahan, a log of woods and combustible materials are collected and put in public place. In day time, ladies worship this and tie sacred thread to take the blessings. In night, people gather around it and perform religious rituals in front of the bonfire. New crop of wheat and oat are offered to fire and taken as Prasad.
3. In the end, holy ash or vibhuti is collected from the fire and applied on the foreheads to keep away evil.
4. Next day, people throw coloured water and gulal on each other. Groups carry drums and other musical instruments, go from place to place, sing and dance.
5. Eating sweets, drinking thandai, frolicking and dancing is part and parcel of this colourful festival. Til ladoos, gujjias, puranpolies, sanjoris, papri and kanji ke bade are the special eatables prepared for Holi.

 
Celebrated since when

1. According to legend, the demon king Hiranyakshyap hated his son Prahlad because he was a devotee of Lord Vishnu. When Hiranyakashyap failed in his attempt to kill his son, he asked his sister Holika who could not be burnt by fire to sit with Prahlad on burning pyre. But Prahlad emerged safe while Holika was burnt to death. To symbolise the burning of the evil Holika, a huge bonfire is lit, the day before Holi (Dhulandi).
2. As a baby, Krishna developed his characteristic dark skin colour because the she-demon Putana poisoned him with her breast milk. In his youth, Krishna was despaired because of his skin colour. His mother, tired of the desperation, asks him to approach Radha and colour her face in any colour he wanted. This he does, and Radha and Krishna became a couple. Ever since, the playful colouring of Radha's face has been commemorated as Holi.
3. Another version attributes Holi as a festival of Lord Krishna who used to play pranks with gopis (milk maids) by showering them with flowers from trees like Kesariya and Tesu (flame of forest). That is how the ritual of playing with colour originated, and to this date.

 
References:
https://en.wikipedia.org/wiki/Holi