When and how did this Kaliyuga start?

[ads1] Kali Yuga कलियुग “age of Kali”, is the last of the four stages (or ages or yugas) the world goes through as part of a ‘cycle of yugas’ (i.e. Mahayuga) described in the Sanskrit scriptures. The other ages are called Satya Yuga, Treta Yuga, and Dvapara Yuga.