yadā - when; deva-ṛṣayaḥ sapta - the seven sages among the demigods; maghāsu - in the lunar mansion Maghā; vicaranti - are traveling; hi - indeed; tadā - then; pravṛttaḥ - begins; tu - and; kaliḥ - the age of Kali; dvādaśa - twelve; abda-śata - centuries [These twelve hundred years of the demigods equal 432,000 earth years]; ātmakaḥ - consisting of.

When the constellation of the seven sages is passing through the lunar mansion Maghā, the Age of Kali begins. It comprises twelve hundred years of the demigods.