गौतम बुद्ध के परिनिर्वाण की ऐतिहासिक तिथि 483 ईसा पूर्व किस आधार पर निर्धारित की गई है?

Which among the following events comes first in chronological order?

The Saka Era, which is also the basis of the Indian National Calendar, was founded in:

The Shaka Era, which is used in the Indian National Calendar, is believed to have commenced in which year?