I don't have any idea on how Saptarṣi constellation passes from one nakshatra to another. Consider the following lines from
When the great sages of the Saptarṣi constellation pass from Maghā to Pūrvāsāḍhā, Kali will have his full strength, beginning from King Nanda and his dynasty.
It says that Nanda dynasty was started when Saptarṣi constellation passed from Maghā to Pūrvāsāḍhā.
I want to know about the frequency of the aforementioned transition. In how many years does this happen generally?