Hatkeshwar Jayanti is an auspicious day observed by the Nagar Community residing mainly in Gujarat and Madhya Pradesh in
Once creation came to a stand still, everyone went to Shiva to find a solution. Shiva asked them to worship him in the form of a Shivling. Brahma created a Shivling made up of gold, i.e Hatak. This shivling was called Hatkeshwar.
The glory and greatness of this manifestation of Shiva is found in the Nagar Chapter of Skanda Purana.
You can read the story of Hatkeshwar Mahadev here in this article.