One verse

Srimad Bhagavatam 12.2.31

12.2.31

यदा देवर्षय: सप्त मघासु विचरन्ति हि । तदा प्रवृत्तस्तु कलिर्द्वादशाब्दशतात्मक: ॥ ३१ ॥

yadā devarṣayaḥ sapta maghāsu vicaranti hi tadā pravṛttas tu kalir dvādaśābda-śatātmakaḥ

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.