The night when Shiva is most accessible — vigil and fast through the four prahars.
The tithi window is the period during which this festival's defining lunar phase is active. Times are in Koothappar local clock.
Maha Shivaratri is the most sacred Shiva night of the year, falling on Phalguna Krishna Chaturdashi. Devotees keep an all-night vigil with fasting, abhishekam of the Shivalingam, and recitation of Shiva mantras through the four prahars (3-hour watches) of the night.
Observed when Chaturdashi tithi is present at Nishita Kala (the midnight watch). When Chaturdashi straddles two civil days at sunrise, the night where Chaturdashi covers nishita is the observance night — typically the day before the sunrise-Chaturdashi day.
Computed for Koothappar (Asia/Kolkata) using local sunrise, sunset and astronomical positions.
Other observances and vrats falling in March 2027, with dates computed for Koothappar.
A more detailed account of Maha Shivaratri — its mythology, regional variations, and rituals — is being prepared.