In this year 2012 Mahavir Jayanthi is on 5th April . Every year Mahavir Jayanthi date is not fixed . It is according to Luni-Solar Jain calender.
Mahavir was born on the thirteen day of the rising moon of Chaitra Masam (month) in 599 BC.
He was founder of Jain Religion
It is a very big festival to all Jainisms.
Father : Siddartha
Mother : Trishala