Thiruvathira or Thiruvathirai or Arudhra Darisanam is a Hindu festival celebrated in Kerala and Tamil Nadu. Thiruvathirai in Tamil means "sacred big wave", using which this universe was created by Lord Shiva about 132 trillion years ago. In Thillai Chidambaram 10 day festival is arranged during Thiruvathirai. It is one of the major events in almost all the Shiva temples in Tamil Nadu and Kerala. The festival is celebrated by Sri Lankan Tamils at Thinnapuram Sundareswarar Temple as well, it is called Eezhathu Chidambaram.

Occurrence of Thiruvathira
It takes place on the full moon night in the Tamil month of Margazhi and this is also the longest night in a year. The stone inscriptions state that the festival has been celebrated on this day for more than 1500 years. Lord Shiva is praised in Tamil by many names; one of them is Athiraiyan, from Thiruvathirai.

Thiruvathira in Tamil Nadu
The Thiruvathira festival is celebrated in Tamil Nadu by various rituals of songs, hymns and dance. The rituals are presented below:

Mantras of Thiruvathira: The Tamil hymns of Manikkavacakar`s Thiruvasagam are chanted in temples instead of Sanskrit mantras. On the very day of Thiruvathirai the idols of Lord Shiva or Mahadeva and his consort Shivagami (Parvati) are taken out of the temple premises for a grand procession. Devotees perform the cosmic dance of Lord Shiva. Neivedhyam (food for God) made for Lord Nataraja on that day is Thiruvathirai Kali.

Songs of Thiruvathira: Sambandar sung in Tevaram during 7th-9th century, how Thiruvathirai was celebrated at Kabaleesharam (present day Mylapore, Chennai). Appar wrote a separate pathigam (10 songs) in Tevaram, in the name of Thiruvathirai Pathigam which describes the importance and celebrations of Thiruvathirai. In 4th Tirumurai he sang about the celebration in Tiruvarur.

Cosmic Dance in Thiruvathira: In this festival people perform the cosmic dance of Lord Shiva. The cosmic dance represents five activities - Creation, Protection, Destruction, Embodiment and Release. In essence, it represents the continuous cycle of creation and destruction. This cosmic dance takes place in every particle and is the source of all energy. Arudra Darshan celebrates this ecstatic dance of Lord Shiva. Lord Shiva is supposed to be incarnated in the form of Lord Nataraja during the Arudhra Darisanam day. Most of the temples around the world with Lord Nataraja and Lord Shiva or Mahadeva as deity perform the Arudhra Darshan.

Thiruvathira in Kerala
The festival is celebrated in Kerala as the birthday of Lord Shiva. Thiruvathira is the nakshatra or "star" as per the Malayalam calendar of Lord Shiva. Another belief is that the festival commemorates the death of Kamadeva, the Hindu God of erotic desire. It is believed that on this day, the Goddess Parvathi finally met Lord Shiva after her long penance and Lord Shiva took her as a saha-dharma chaarini (equal partner). Both Parvathi and Shiva present this ideal to devotees in the form of Ardha-Nareeshawara (half male, half female form).

Devotees generally take fasting during this festival. And food only includes the "Thiruvathira Puzhukku", a delightful mix of tuber vegetables. They perform the Thiruvathirakali dance, which is performed by women in the accompaniment of Thiruvathira Pattu. It is a folk song, which narrates the long penance of Goddess Parvati for Lord Shiva. This festival is also known as Kerala"s own version of "Karva Chauth". It is a festival where women take fast for their husband"s well being.