Vishwakarma Day is celebrated to worship Vishwakarma, a Hindu god. Vishvakarma was the divine architect, and one of the fourteen precious things born of the Samudra manthan. He constructed the holy city of Dwarka where Lord Krishna ruled, the Maya Sabha of the Pandavas, and was the creator of many fabulous weapons for the gods. He is also called the divine carpenter, is mentioned in the Rig Veda, and is credited with Sthapatya Veda, the science of mechanics and architecture.
It is celebrated on September 16 or 17 (in some states in India, like Karnataka, West Bengal, Bihar, Jharkhand, Orrisa, and Tripura). The festival is observed primarily in factories and industrial areas, often on the shop floor. Vishwakarma is known to be the divine engineer since the Puranic age. As a mark of reverence he is worshipped not only by the engineering and architectural community, but also by all professionals. Artisans, craftsmen, mechanics, smiths, welders, industrial workers, factory workers, and workers of all kinds worship Lord Vishwakarma on this day and pray for a better future, safe working conditions, and above all success in their respective fields. Workers also pray for the smooth functioning of various machines. It is customary for craftsmen to worship their tools in His name. Workers refrain from using the tools while doing so.
Special statues and pictures of Lord Vishwakarma are normally installed in every workplace and factory. All workers gather in one common place and perform the puja. In many factories owner and employees worship vishwakarma ji for the good working of their works.
As per Indian mythology Vishwakarma puja (reverence) is also celebrated a day after Diwali, along with Govardhan Puja.