The Vikram era, or Vikram samvat is an Calendar System(mostly followed in Hinduism and Sikhism from people of Indian Subcontinent) starting in 57 BC. The Vikram Samvat calendar starts half a century before the Gregorian calendar and works on an Indian calendar cycle.
The story of this event is told by a sadhu (Jain monk) called Mahesara Suri.
The powerful king of Ujjain, called Gardabhilla, kidnapped a sadhvi (Jain nun), who was the sister of the sadhu. The sadhu went to the Saka King to get help, and in the end, the Saka King beat Gardabhilla and captured him and made him a prisoner. But in the end, Gardabhilla was forgiven and run away to a forest, where he was killed by a tiger.
Later on Vikramaditya invaded Ujjain and drove away the Sakas. To commemorate this event he started a new era called the Vikrama era.