In the traditional Hindu calendar followed in North India, Sawan is the fifth month. The month is considered an extremely holy and sacred month in Hinduism. While the entire month is dedicated to the worship of Hindu deity Lord Shiva, the Mondays of the month are considered especially sacred. A Monday in the month of Sawan is known as Sawan Somwar.
In 2018, the Sawan month commences on July 10 and ends on August 7. The dates for Sawan Somwar in the states of Bihar, Himachal Pradesh, Madhya Pradesh, Punjab, Rajasthan and Uttar Pradesh in 2018 are July 10, July 17, July 24, July 31 and August 7. For Andhra Pradesh, Goa, Gujarat, Karnataka, Maharashtra and Tamil Nadu, the dates are July 24, July 31, August 7, August 14, and August 21. On these auspicious Mondays, devotees of Lord Shiva should make it a point to visit Shiva temples, and make offerings to Him and chant prayers.
The difference in dates are due to the fact that two distinct lunar calendars are followed in different states of the country. While Bihar, Himachal Pradesh, Madhya Pradesh, Punjab, Rajasthan and Uttar Pradesh follow the Purnimant Calendar, Andhra Pradesh, Goa, Gujarat, Karnataka, Maharashtra and Tamil Nadu follow the Amavasyant Lunar Calendar.
In addition to Sawan Somwar, mangalwar (Tuesdays) are dedicated to Lord Shiva’s consort, Goddess Parvati. Known as Mangal Gauri Vrat, many observe fast on the Tuesdays of the Sawan month as well.
According to Hindu mythology, it was in the month of Sawan that the Samudra Manthan took place. As the demons and the gods churned the ocean, out from the ocean emerged fourteen items of divinity. A deadly poison also came out, and it was considered the death and destruction of the entire world. Lord Shiva took responsibility and swallowed the poison. However, the poison could not pass his throat, and as a result, it accumulated there and turned it blue, which is the origin behind one of his nicknames, Neelkantha (blue throat).