The night in Maagha month with chaturdasi is the Maha Shivratri. This is time that Parama Shiv had drank the world destroying poison that came out during the churning of the ocean for Amrit by Devas and Asuras.
Even Lingodhbhava occurred during the thithi only. It is an auspicious occasion to visit Shiv temples and pray to Lord. In the night people do jagaran or vigil by singing bhajans of the Lord. Modern versions people go to movies and film theaters have very late night shows with some showing religious movies. In all Shiv temples across the country the festival is celebrated with great fervour.
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महाशिवरात्रि - Mahashivaratri - Hindi