Vishwakarma Puja, also known as Vishwakarma Day, is celebrated every year on the 17th of September and the day after Diwali. On these days, Lord Vishwakarma is worshipped, who alone constitutes the entire history with which this festival is linked. According to the religious texts, Lord Vishwakarma is known as "Devashilpi" or "The Architect of Gods" and considered to be the sole architect and craftsman of Triloka or The Tripartite Universe - heavenly realms and their worlds, the mortal realms and their worlds, and the netherworldly and other celestial realms and worlds. His master craftsmanship however is deemed to be limitless as it is believed that he also created the flying chariots and weapons of Gods that were used in the mythological times, including the sacred weapon of Lord Indra known as Vajra which is made from the bones of sage Dadhichi. He is also believed to have given divine attributes to each of the weapon he created.
The sacred Hindu texts also describe many of Lord Vishwakarma's architectural marvels, towns and palaces for the Gods, through the four ages. Some of them are Swarga (Heaven) in the Satya Yuga; Sone ki Lanka (Golden Lanka), where demon king Ravana dwelled in the Treta Yuga; the city of Dwarka, the capital of Lord Krishna in the Dwapara Yuga; the town of Hastinapur, the capital of Pandavas and Kauravas from the Mahabharata; and the town of Indraprastha for the Pandavas. Even the texts of Mahabharata describe Lord Vishwakarma as "The Lord of Arts, Executor of a thousand Handicrafts, the Carpenter of the Gods, the most eminent of Artisans, the Fashioner of all ornaments ... and a great and immortal God..." Represented in idols and images with a water pot, the Vedas, a noose, and craftsmen's tools in each of his four hands, he is the divine engineer of the world.
The historical relevance related to Vishwakarma Day gains more weightage as not only is Lord Vishwakarma associated with creation but also with the manifestation of the sciences of industry to the humankind. It's because of this history that he is much revered by the devotees, more so by professionals like engineers, architects, artisans, craftsmen, weavers, mechanics, smiths, welders, industrial workers, and factory workers who make their living through their craftsmanship. And therefore on Vishwakarma Day, pandals are set up inside the premises of industries and factories and inside these pandals, images and idols of Lord Vishwakarma are established. The whole workforce, along with each employee's and worker's family, celebrates Vishwakarma Puja in unison. Even the tools, particular to each person's relative field, are worshipped in the name of Lord Vishwakarma and aren't used throughout the day. It's their day off! Then after the Puja is performed and the ritual is complete, Prasad (offerings) are distributed among everybody.