Mahashivratri means “the night of Lord Shiva” and falls on Falgun Vad Chaudas. This day is celebrated in honour of Lord Shiva, and marks his marriage to Parvatiji. In Shikshapatri, Bhagwan Swaminarayan states that Vedas declare Narayan and Shiva to be equal, as Lord Narayan is the protector of life while Lord Shiva is the destroyer. Moreover the 4 Vedas state that the two are considered to be one. They share a single body and soul, just as a husband and his wife have the same body and soul. Shrimad Bhagvad states that those that see Brahma, Vishnu and Shiva as one being attain peacefulness. Because of this great significance, Shivrati is regarded as equally important as Ramnavmi and Janmashtmi, and a fast is observed on this day. 

The reason behind this can be found in the Mahabharat within the story of King Chitrabhanu and his previous life. As the king sat in his palace, observing the fast along with the entire town, a sage asked the king the purpose of his fast. The king went on to explain that he had a gift – that which enabled him to remember incidents from his previous lives. In his last life, the king was a hunter in Varanashi and he made his keep by killing and going on to sell birds and animals. On one particular occasion, he was out venturing the forest, when darkness fell. He was unable to return home and sought to find shelter for the night, such was his luck that he found a Bilva tree, which he climbed and rested. He had caught a deer, and so tied it at the foot of the tree. Anxiety refused to leave his mind that night, as he continuously worried what his poor family would eat. Without realising, he began to pluck leaves from the tree and dropped them to the ground beneath him. The next morning, having sold the deer and bought food for the family, he returned home and was about to break his fast when a stranger approached him. Out of courtesy, he stood up, offered the food to the stranger and then sat to eat again. 

At the time of his death, he was visited by two messengers of Lord Shiva, sent especially from Kailash, and it was only then that he learnt of his unconscious worship to the great deity on the night of Shivratri. For as he wept and dropped leaves to the ground, little did he know that there was a Lingam just beneath, and with the drop of each leaf, he shed the pure sorrow of his family, and he also fasted day and night, although he did not realise it, simply through the absence of food. As a result, the king spent a blissful time in the divine abode of Lord Shiva, before returning to be reborn as the King Chitrabhanu. 

Bhagwan Swaminarayan also instructs householders in the Shikshapatri to offer Lord Shiva leaves from the Bilva tree – bilva leaves because they are symbolic of the trident that Lord Shiva holds. By making this offering, one can improve on their after life, and are able to attain anything in this life and the next, however not moksha, as only Bhagwan Swaminarayan himself is able to free you from the eternal cycle of life and death. 

The Satsangi Jeevan states that on the night of Mahashivratri, Bhagwan should be dressed with brightly coloured garments, and His abhishek should be performed in the evening. Also, a pooja of bilva leaves should be done to Lord Shiva, and kheer and savoury dishes should be offered to Bhagwan, along with the performance of loving kirtans in his honour.