The National Calendar of India is based on the era known as the Saka era. This era began on March 22, 78 AD, and is named after the Shaka dynasty, which ruled over the western part of India during that time. The Saka era is used as the reference point for the National Calendar of India, which is an official calendar used by the government for scheduling purposes and public holidays. The other options provided in the question are not correct. The Vikrama era, also known as the Vikram Samvat, is a separate calendar system used in India, while the Kali era is not associated with the National Calendar.