yada -- when; deva-rishayah sapta -- the seven sages among the demigods; maghasu -- in the lunar mansion Magha; vicaranti -- are traveling; hi -- indeed; tada -- then; pravrittah -- begins; tu -- and; kalih -- the age of Kali; dvadasa -- twelve; abda-sata -- centuries [These twelve hundred years of the demigods equal 432,000 earth years]; atmakah -- consisting of.

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