SB 1.15.36
yada mukundo bhagavan imam mahim
jahau sva-tanva sravaniya-sat-kathah
tadahar evapratibuddha-cetasam
abhadra-hetuh kalir anvavartata
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
When the Personality of Godhead, Lord Krsna, left this earthly planet in His selfsame form, from that very day Kali, who had already partially appeared, became fully manifest to create inauspicious conditions for those who are endowed with a poor fund of knowledge.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The influence of Kali can be enforced only upon those who are not fully developed in God consciousness. One can neutralize the effects of Kali by keeping oneself fully under the supreme care of the Personality of Godhead. The Age of Kali ensued just after the Battle of Kuruksetra, but it could not exert its influence because of the presence of the Lord. The Lord, however, left this earthly planet in His own transcendental body, and as soon as He left, the symptoms of the Kali-yuga, as were envisioned by Maharaja Yudhisthira prior to Arjuna’s arrival from Dvaraka, began to manifest, and Maharaja Yudhisthira rightly conjectured on the departure of the Lord from the earth. As we have already explained, the Lord left our sight just as when the sun sets it is out of our sight.