some more details about time

Kaliyaga stated from B.c 3102 feb17th midnight.
as per our mythogoly on the last day of dwabarayug Lord Krishna left to vaikunda and Uthishtra to mooksha.Another opion is Uthistra crowned as aking on the first day of Kaliyuga. From that day till vikrama saga first day is known as Uthistra sahaptium.( upto B.C 58)

Saptarishi era:
It has 2700 years. It is divided into 27.Each has 100year. as the saparishi mandala travel through each star (27X100).Asper this teory Kaliyuga startes when saptarishi was near Magha (மகம்) for 75 years.That means B.C. 4077.This is the oldest theory.

Jupiter circle. Jupiter takes 432.6 days for one round in space. there are 2 type of calculation 12years, 60years.