Overview
Shivratri, also known as Maha Shivaratri, is a Hindu festival observed annually in honour of the deity Shiva. It falls between February and March, on the chaturdashi (14th lunar day) of the krishna paksha (waning moon) in the month of Magha or Phalguna. While the month may differ between the Purnimanta and Amanta calendars followed in different regions, the festival is observed on the same lunar night across India.
According to tradition, the festival commemorates the marriage of Shiva and Parvati, as well as the occasion when Shiva is said to have performed his ritual dance, the tandava. It is regarded as a significant festival in Hinduism and is associated with the theme of "overcoming darkness and ignorance" in one's life and in the world. The festival is believed to have originated in the 5th century BCE.
Observances include remembering Shiva, chanting prayers, fasting, and meditating on ethical values such as honesty, non-injury to others, charity, and forgiveness, alongside contemplation on the discovery of Shiva. Ardent devotees keep a vigil through the night. Others visit Shiva temples or undertake a pilgrimage to the Jyotirlingam shrines associated with Shiva.
In the Kashmir region, within the tradition of Kashmir Shaivism, the festival is known among devotees as Har-ratri, or in its phonetically simpler forms, Haerath or Herath.
References
Adapted from the English Wikipedia article on Maha Shivaratri.