"The great night of Shiva," kept with a night-long vigil through all four praharas, fasting, and offerings of bael leaves and milk to the Shiva lingam. One telling holds this the night Shiva swallowed the halahala poison from the churning of the ocean to save creation — his throat turning blue, and devotees staying awake in solidarity ever since.
फाल्गुन कृष्ण चतुर्दशी
A second tradition holds this as the night of Shiva and Parvati's wedding, celebrated as a cosmic union rather than only a night of penance and vigil.
Temples at all twelve Jyotirlingas hold their largest annual crowds on this night; some devotees keep a fully waking vigil, jagran, through all four praharas without sleep.