Pongal is a festival by the Indian state of Tamil nadu .Tamils refer to pongal as "Tamizhar Tirunal "(meaning 'the festival of Tamils') Traditionally this is celebrated at Harvest time, it is a celebration of the prosperity associated with the harvest by thanking the God of Rain ,Sun, and the farm animals that have helped during cultivation and harvest. This festival is celebrated in a grand manner in villages .Usually this pongal festival is celebrated four days,and it falls on January 12 - 15 every year.
The four days are called as :
1.Bhogi
2.Surya Pongal
3.Maatu Pongal
4.Kaanum Pongal
1.Bhogi
2.Surya Pongal
3.Maatu Pongal
4.Kaanum Pongal
The first day, Bhogi is celebrated in honour of Lord Indira. On this day all the 
houses are cleaned and decorated with kolams and they throw away all the old things in the house into a fire made of wood and cowdung.This is like a bonfire, and the girls will dance and sing around the bonfire,praising the Gods for giving them good harvest.
houses are cleaned and decorated with kolams and they throw away all the old things in the house into a fire made of wood and cowdung.This is like a bonfire, and the girls will dance and sing around the bonfire,praising the Gods for giving them good harvest. 
The second Day, Surya Pongal is dedicated to the Sun God.It is the day actually 
the celebration begins and it is also the first day of the Tamil month "Thai Maasam". In the Villages,people gather in the courtyard and prepare the Pongal Prasadam in the open.They buy new pots for preparring , which is decorated with flowers, Turmeric plant,mongo leavesand they offer sugarcane and pongal to the God of sun. It is a tradition to shout of "Ponggalo Ponggal " and blowing the "Counch (Sangu) " , a custom practiced during the festival to announce it will be a year blessed with good tidings.
The third day of Pongal is dedicated to cattle and is called as Mattu Pongal.
The third day, Mattu Pongal has an association with the legend of Lord Shiva and h
is Nandi (Basava), the bull. Lord Shiva asked his bull to go to the earth and deliver his message to the people to have an oil massage and bath daily and to eat food once in a month. Mistakenly Basava announced to have an oil massage and bath once in a month and to eat food daily.Enraged Shiva cursed Basava and said that due to this mistake ther would be lack of grains on Earth. He banished the bull to live on earth forever and help people plough the fields.
the celebration begins and it is also the first day of the Tamil month "Thai Maasam". In the Villages,people gather in the courtyard and prepare the Pongal Prasadam in the open.They buy new pots for preparring , which is decorated with flowers, Turmeric plant,mongo leavesand they offer sugarcane and pongal to the God of sun. It is a tradition to shout of "Ponggalo Ponggal " and blowing the "Counch (Sangu) " , a custom practiced during the festival to announce it will be a year blessed with good tidings.The third day of Pongal is dedicated to cattle and is called as Mattu Pongal.
On this day the cattles are washed well and their horns are painted and covered with shinning and multicoloured beads, tinkling bells and flower garlands are tied round the necks.On this day Jallikattu - a Bull festival is held in Madurai, Trichy,Tanjore.Bundles of money are tied to the horns of bulls which the villagers tries to remove it. Whoever removes it will be awarded the money as a prize in winning the competition.
On this day Women offer prayers for the wellbeing of their brothers.The woman perform the ritual before bathing in the morning, they assemble in the courtyard and in the turmeric plant leaf they place the riceballs of Red, Yellow, white, (Rice is mixed with kumkum, manjal, curd respectively and made into small balls.) Sweet pongal, sugarcane and pray for the house and family of their brothers should Prosper.
While praying the God, They tell these lines. :
காக்காய்ப்பிடி வைத்தேன்; கனுப்பிடி வைத்தேன்;காக்காயகளுக்கெல்லாம் கல்யாணம், .காக்காய்களின் கூட்டம் போல எங்கள் குடும்பமும் எல்லோரும் ஒர்றுமையாக வாழ வேண்டும்.
காக்காய்ப்பிடி வைத்தேன்; கனுப்பிடி வைத்தேன்;காக்காயகளுக்கெல்லாம் கல்யாணம், .காக்காய்களின் கூட்டம் போல எங்கள் குடும்பமும் எல்லோரும் ஒர்றுமையாக வாழ வேண்டும்.
The Fourth day is called as Kannum Pongal. On this day Surya pooja is done by offerring sakarai pongal, sugarcane and coconuts , for getting plentiful harvest in the forthcoming year. All the people on this day travel to see other family members and pay homage to the elders.
THE LEGEND OF PONGAL FESTIVAL :
The first day , Bhoggi has an association with legend of Lord Indra and Lord Krishna
. In early days people used to worship Lord Indira, King of the deities.This honor given, made him full of pride and arrogance.When child Krishna came to know about this ,he thought of a plan to teach Indira a lesson. He pursuaded his cowherd friends to worship Mount Govardhana rather than Lord Indira. The angered Lord Indira set forth the clouds to generate non-stop rain, thunder. As per the tale, Krishna lifted the huge Govardhan mountain with his little finger ,to protect the cowherds ,cattle and all the people.
. In early days people used to worship Lord Indira, King of the deities.This honor given, made him full of pride and arrogance.When child Krishna came to know about this ,he thought of a plan to teach Indira a lesson. He pursuaded his cowherd friends to worship Mount Govardhana rather than Lord Indira. The angered Lord Indira set forth the clouds to generate non-stop rain, thunder. As per the tale, Krishna lifted the huge Govardhan mountain with his little finger ,to protect the cowherds ,cattle and all the people.The rain continued for three days and Krishna was protecting all of them continously..and atlast Indira realised his mistake and the divine power of Krishna.Since then Krishna allowed to let the Bhogi celebration continue in honour of Indira.
The third day, Mattu Pongal has an association with the legend of Lord Shiva and h
is Nandi (Basava), the bull. Lord Shiva asked his bull to go to the earth and deliver his message to the people to have an oil massage and bath daily and to eat food once in a month. Mistakenly Basava announced to have an oil massage and bath once in a month and to eat food daily.Enraged Shiva cursed Basava and said that due to this mistake ther would be lack of grains on Earth. He banished the bull to live on earth forever and help people plough the fields. 
Thus, mattu pongal has an association with the cattle. This is how Pongal is being celebrated in Tamilnadu.
Sources : Wikipedia .
