Indian Hindu lunar calender is cyclical. Four ages, Krita, Treta, Dwapara and Kali are called yuga.
Kalpa is the largest unit of time consisting of 4000 yugas. Kalpas are named and now we are in Shweta Varaha Kalpa (White Pig Kalpa). Next unit is 14th part of Kalpa called Manvantara. Now we are in Vaivaswata Manvantara.
Each yuga consists several 60 named year groups called Samvatsaras. On March 19th 2007 we will enter the year 1929 SE or 1929 of the Shalivahana Saka (Saka Era). This year is named Sarvajit, one of the 60 samvatsaras.
Yugadi (Ugadi) marks the first day of the calender for people in Karnataka, Andhra Pradesh, and Maharastra (where it is called Gudipadva).
The first day of the season called vasanta Rutu (spring one of the six seasons in India) and the month Chaitra. Padya is a vernacular name for Pratipada the first day.
Traditionally Yugadi is celebrated by sharing a mixture of Jaugary and Neem leaves.