Śrīmad-Bhāgavatam 12.2.31
యదా దేవర్షయ: సప్త మఘాసు విచరన్తి హి ।
తదా ప్రవృత్తస్తు కలిర్ద్వాదశాబ్దశతాత్మక: ॥ ౩౧ ॥
yadā devarṣayaḥ sapta
[yadaa devarshayah sapta]
maghāsu vicaranti hi
[maghaasu vicharanti hi]
tadā pravṛttas tu kalir
[tadaa pravrittas tu kalir]
dvādaśābda-śatātmakaḥ
[dvaadashaabda-shataatmakah]
Word-for-word
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.
Blended reading (Sanskrit + English inline)
yadā devarṣayaḥ sapta
yadā
when
deva-ṛṣayaḥ sapta
the seven sages among the demigods
maghāsu vicaranti hi
maghāsu
in the lunar mansion Maghā
vicaranti
are traveling
hi
indeed
tadā pravṛttas tu kalir
tadā
then
pravṛttaḥ
begins
tu
and
kaliḥ
the Age of Kali
dvādaśābda-śatātmakaḥ
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.
Gauḍīya Ācāryas
Viśvanātha Cakravartī Ṭhākura
Gauḍīya
Translation
When the seven sages pass into the constellation Maghā, the age of Kali begins. Kali-yuga comprises twelve hundred years of the devatās.
When the seven sages enter Maghā constellation and Kṛṣṇa disappears, the next moment after that Kali-yuga begins. Twelve hundred years of the devatās includes the two sandhyās as well. [Note: There is a sandhyā at the beginning and end of each yuga. The proportions are .1 from the beginning portion, .8 for the middle portion and .1 for the concluding portion of the yuga.]
My note
Source: vedabase.io