Maha Shivratri, the "great night of Shiva," is observed with a daytime fast and a vigil through the four watches of the night, each marked by a fresh bathing of the Shiva lingam with water, milk, honey and bilva leaves. Temples stay open through the night and devotees recite the names of Shiva, the Rudram, the Mahamrityunjaya Mantra, the Shiva Panchakshara Stotra and the Lingashtakam. Some connect the night to the marriage of Shiva and Parvati, others to Shiva's appearance as an endless column of light.
The festival falls on the fourteenth tithi (Chaturdashi) of the waning fortnight of the month of Phalguna in the Purnimanta calendar, which is the Chaturdashi in Magha by the Amanta reckoning. The central worship is fixed to the Nishita period, the middle of the night, so its timing depends on the city's sunset and sunrise.
Alongside this annual night, a Masik Shivratri is kept every lunar month on the same tithi.