Aadi pooram is a festival celebrated in Tamilnadu during Aadi month (Jul mid-Aug mid) on Pooram nakshatram day.
In perumal temples, the day is celebrated by performing Andal Thirukalyanam.
People also do poojas with bangles and distribute those to women.
Andal story:
Periyazhwar used to make garlands to decorate Vishnu idol in temple. He was ardent devotee of perumal (Lord Vishnu) and used to perform his duty with complete devotion. He had no children and prayed to Vishnu to bless him. On aadi pooram day he found a baby girl near the Tulasi plant in the temple. He thought it was Bhudevi (Mother Earth) who has come in the form of baby. He took the baby girl and named her Kothai and grew her up. Kothai grew up helping her father in making garland tying together the flowers from the garden, listening to stories about Krishna from her father.
As she listened to stories of Krishna, she developed a deep involvement in the stories and developed a kind of devotion to Krishna, a level higher than a normal devotee. She would make garland of perumal everyday and wear it for herself and then give it to her father to decorate perumal statue in the temple. Her father was not aware that Kothai wears the garland before handing it over to her father, until he saw her doing it one day. He was shocked seeing it and thought his daughter is doing something very wrong according to the rules to be followed while offering anything to god. So, he made a different garland to offer to perumal, however, for some reason he could not offer it to perumal. He was very much worried that perumal was not accepting his offering. Perumal appeared in his dream that night and told him that he was happy with the garland that Kothai made and wore and offered him and Periyazhwar need not think this as a mistake and that the lord accepts Kothai's devotion this way.
When Kothai was 15, her father thought she was old enough for marriage and looked for a bride. Kothai on the other hand had resolved to marry Ranganathar (Lord Vishnu's form in Srirangam temple) and was very stubborn about her decision. Lord Vishnu appeared in Periyazhwar's dream and asked Periyazhwar to arrange for marriage for his daughter with him. Periyazhwar arranged for the marriage. Andal dressed up for the wedding, went long with her father to Ranganathar temple and united with the Lord in the presence of her father and the others.
