The Hindu literature of Puranas refer to the events anterior to Mahabharata in the past tense and the event posterior to Mahabharata in future tense.
Unfortunately the only dateable archeological evidence ever found mentioning Hindu gods in pre Buddha era is the Mitanni evidence. Navagrahas occupy a very important role in the Hindu calendar and worship. A Hindu devotee pays his respects to Navagrahas by circumambulating them nine times.
The absolute astronomical evidence helps in accurately dating the event.
The absolute position of moon helps to point to a specific day.
Thus absolute position helps in establishing the absolute chronology.
When the position of the navagraha is a simple observation with respect to its position in the observable sky and horizon then it is a relative astronomical evidence.