Maha Shivaratri — “the great night of Shiva” — falls on the Krishna Chaturdashi (the fourteenth night of the waning moon) in the month of Magha–Phalguna, the night just before the new moon. Unlike festivals of light and colour kept by day, Shivaratri is a night observance: a fast through the day and an all-night vigil (jagaran) spent in the worship of Shiva, the auspicious one.
The four prahars — the night in four watches
The night of Shivaratri is traditionally divided into four prahars (watches of roughly three hours each). In each watch the Shiva linga is given an abhisheka — a ritual bath — with a different sacred substance, followed by worship, so that the whole night becomes one continuous puja.
First prahar — abhisheka with milk (kshira)
The vigil opens after sunset. In the first watch the linga is bathed with milk, the symbol of purity and nourishment, while the worshipper offers flowers and chants the name of Shiva. In many traditions the four prahars are also associated with the four directions and the four Vedas.
Second prahar — abhisheka with curd (dadhi)
In the second watch the linga is bathed with curd (yoghurt). Worship continues with bilva leaves, incense and lamps, the household staying awake together. The repetition of the abhisheka through the night keeps the mind gathered on a single point.
Third prahar — abhisheka with ghee and honey
The third watch brings the bath of ghrita (clarified butter) and madhu (honey) — offerings of light and sweetness. This middle of the night is often kept with the recitation of the Shri Rudram (the Rudra-prashna of the Yajurveda) and the Mahamrityunjaya mantra.
Fourth prahar — abhisheka with water (jala)
In the final watch before dawn the linga is bathed with pure water, the simplest of all offerings, recalling that Shiva is Bhola — pleased by sincerity rather than display. The vigil closes near sunrise, and the fast is broken the following day.
Legends of the night
Several well-loved stories are remembered on Shivaratri, each adding a layer of meaning to the vigil — why the night is kept, and what is being honoured in it.
Lingodbhava — the infinite pillar of light
When Brahma and Vishnu disputed which of them was greater, a fathomless pillar of fire — the jyotirlinga — appeared between them. Brahma flew upward as a swan and Vishnu dived down as a boar (Varaha), each seeking an end of it, yet neither could reach top or bottom. The endless column revealed Shiva as the formless source beyond both creation and preservation. This is remembered especially at the midnight hour of Shivaratri.
Neelakantha — the night Shiva drank the Halahala
During the churning of the ocean of milk (Samudra Manthan), the deadly Halahala poison rose first and threatened to consume all creation. To save the worlds, Shiva gathered the poison and held it in his throat, which turned blue — and so he is called Neelakantha, the blue-throated one. Devotees keep awake with him through the night, honouring the compassion that drank the world’s poison.
The hunter and the bilva tree
A poor hunter, lost in the forest and afraid of beasts, climbed a bilva (bel) tree for the night. To stay awake he plucked its leaves and dropped them down, one by one — and beneath the tree, unseen, stood a Shiva linga, upon which the trifoliate bilva leaves fell all night long. Fasting (because he had eaten nothing), keeping vigil, and offering bilva without even knowing it, the hunter unknowingly performed the perfect Shivaratri worship and was blessed. The story teaches that sincere devotion is received whatever the worshipper’s station.
How it is observed
Upavasa — the fast
Many keep a full or partial fast through the day and night, some taking only water, fruit and milk. The lighter body supports the wakeful, inward turn of the vigil; the fast is broken the next morning after the night’s worship.
Bilva-patra — the bel leaf
The three-lobed bilva leaf is the offering most dear to Shiva, its three leaflets read as the three eyes, the three gunas, or the trident. Bilva, water, and sincerity are held to be enough; elaborate materials are not required.
Rudrabhishekam — the sacred bath
The linga is bathed (abhisheka) with the substances of each prahar — milk, curd, ghee and honey, and water — while the Shri Rudram is chanted. The flowing abhisheka is the heart of the night’s ritual.
Japa — Om Namah Shivaya and Mahamrityunjaya
The five-syllable mantra Om Namah Shivaya (the Panchakshara) and the Mahamrityunjaya mantra of the Rigveda are repeated through the watches, steadying the wakeful mind on the name and form of Shiva.
Jagaran — the all-night vigil
The defining observance is to stay awake (jagaran) the whole night in worship, song and remembrance. The wakefulness is itself the sadhana — a night of alertness turned wholly toward the auspicious one.
Educational overview. Tithi, fasting rules and the exact sequence of the prahar puja vary by region, sampradaya and temple; follow your family tradition or local panchang for observance.