In Jainism, Mahavir Jayanti is the most important religious holiday. It celebrates of the birth of Mahavira, the last Tirthankara. He was born on the 13th day of the rising moon of Chaitra, in either 599 BC or 615 BC (depending on religious tradition).
The holiday occurs in late March or early April on the Gregorian calendar.
In 2005, Mahavir Jayanti falls on April 22.