Shiva Shayana Vrata or Shiva Sayanotsav is an auspicious vrata observed to mark the Yoganidra (meditative sleep) of Lord Shiva for four holy months, Chaturmas. Shiva Shayan Vrata begins on Ashada Purnima, the day which is also celebrated as Vyas Purnima or Guru Purnima.
Shiva Sayana Vratam is a main festival for Shaiva sect of people. In 2017, Shiva Sayana Vrata date is July 9.
Puranas described that as similar to Lord Vishnu who sleeps on Ksheer Sagar for four months, Lord Shiva also goes into sleep for four months. Shiva ties all sins of with his ‘Jhata Jhoot (hair) and sleeps on tigers skin. Hence, it is called as Shiva Shayanotsavam. During Shiva Shayanotsav, four holy months, Lord Shiva demolishes sins and evil and establishes wellness and prosperity.
The rituals of Shiv Sayanotsav include, Shiva Dolotsavam or Shiv Dolotsav is celebrated. Reciting Shiva Purana is highly meritorious. Lord Shivas idol is swung in a cradle during Shiva Dolotsav.