(Courtesy: Ajinkya Sudhir Umbarkar, inspired by the suggestion of, Shri Prabhakar Phadnis)
Photos below show how Arundhati and Vasistha would appear crossing the meridian line.
At the center-top, Vasistha (bigger white dot) is to the left of Arundhati (small white dot) crossing the meridian. Their motions are anticlockwise, and thus from right to the left.
Thus, Vasistha is seen walking ahead of Arundhati. The year is 2015 CE. (our times).
This was the case 1000 years ago,
This was the case 2000 years ago
This was the case 3000 years ago
This was the case 4000 years ago
This was the case 5000 years ago
This was the case 6000 years ago
Only when one goes backwards in antiquity, prior to 4508 BCE, the picture changes.
Now Arundhati (small white dot) is to the left of Vasistha (big white dot), both walking Anticlockwise (and thus from right to the left). The vertical line represents the meridian. The year is 5561 BCE.
Arundhati would have appeared to walk ahead of Vasistha, over a ~6000 year period (only instance of this happening in the vast past of human existence), beginning with 11091 BCE and ending with 4508 BCE.
This time interval is the, now famous, EPOCH OF ARUNDHATI.