The Symptoms of Kali-yuga

yadā devarṣayaḥ sapta

maghāsu vicaranti hi

tadā pravṛttas tu kalir

dvādaśābda-śatātmakaḥ

(Śrīmad Bhāgavatam 12.2.31-34)

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. 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. Those who scientifically understand the past declare that on the very day that Lord Śrī Kṛṣṇa departed for the spiritual world, the influence of the age of Kali began. After the one thousand celestial years of Kali-yuga, the Satya-yuga will manifest again. At that time the minds of all men will become self-effulgent.