The festival of Chithira Pournami is celebrated on the Full Moon day of the Tamil month of Chithirai (April-May) when the star Chithirai joins it. It is considered that it is a festival conducted to propitiate Chitragupta, the chief assistant and recording angel of Lord Yama. An account of all virtues and vices with which human beings are associated during their life on earth is recorded by this angel, to be read before Lord Yama on the judgment day. The celebration of this festival is, therefore, intended to act as a check on our conduct in life due to the reminder that all of us will be called upon to explain our conduct even after death.
This festival would appear to have been celebrated from very ancient times in Tamil Nadu having been known in those days as Indra Vizha or a festival dedicated to lord Indra. There is a reference to the Indra Vizha in Tamil work Silappadhikaram. But it has ceased to be celebrated as such for a long time and there is no account of its celebration within living memory.
According to a legend, Brihaspathi, the preceptor, philosopher and guide of Lord Indra once got offended with Indra due to an act of disrespect shown to him and left his court. When the guidance of the revered Guru was withdrawn, Lord Indra committed various errors of omission and commission and when such instances became numerous, he was deeply upset and repented very much for his rashness. Repentance being expiation for all sins, Guru pardoned him and rejoined his old position. Indra thereafter undertook a pilgrimage to all important shrines to atone for sins. After visiting various places, he came to a forest where he felt a sudden form of energy, wisdom and a peace of mind. He attributed this miracle to a glorious Sivalingam situated under Kadamba tree near a beautiful tank. He had a temple built immediately at the site installing the Lingam and another temple for the divine mother. After completing the construction of the shrines, Indra found that flowers were not available anywhere nearby for worship. By divine grace, he found golden lotuses suddenly floating in large quantities in the tank; he collected them and performed the worship to his great satisfaction. It is believed that the place where he built the shrine was Madurai and the Lingam installed by him was the Lord Sundaresar, and that the incident happened on the Full Moon day in the morning of Chithirai. This accounts for the simultaneous origin of the city and the temple of Madurai and it is still the belied that on the anniversary of this dat, Lord Indra still comes to Madurai to worship the deities.
Now Chithira Pournami festival is celebrated in Madurai Meenakshi temple under the name Chaitrotsavam.