The Hindu CalendarThe Hindu calendar is based on the age of Lord Bramha, the Creator of Universe. The life span of Lord Bramha is 100 years. His age now is 51 years. Each day of Lord Bramha is designated by a Kalpa. Each Kalpa comprise of 14 Manus and each Manus consist of 71 Mahayug. 1000 such Mahayugs completes Lord Bramha's 1 day. At present, we are in the 28th Mahayug.
One Mahayuga comprises of :
1. Krutayug = (432,000 X 4) years
2. Tretayug = (432,000 X 3) years
3. Dwaparyug = (432,000 X 2) years
4. Kaliyug = (432,000 X 1) years
We are passing the Kaliyug today, which started in the year 3102 B.C.
The Yugas are further sub-divided into 60 year cycles. The current cycle began on March 30, 1987 and will end in April 2047.
The religious ritualistic activities are mainly based on the Lunar Calendar.
However, some regions of Bharat(India) follow the Solar Calendar.