One verse

Srimad Bhagavatam 3.11.18

3.11.18

मैत्रेय उवाच कृतं त्रेता द्वापरं च कलिश्चेति चतुर्युगम् । दिव्यैर्द्वादशभिर्वर्षै: सावधानं निरूपितम् ॥ १८ ॥

maitreya uvaca krtam treta dvaparam ca kalis ceti catur-yugam divyair dvadasabhir varsaih savadhanam nirupitam

maitreyah uvaca
Maitreya said
krtam
the age of Satya
treta
the age of Treta
dvaparam
the age of Dvapara
ca
also
kalih
the age of Kali
ca
and
iti
thus
catuh-yugam
four millenniums
divyaih
of the demigods
dvadasabhih
twelve
varsaih
thousands of years
sa-avadhanam
approximately
nirupitam
ascertained.

Maitreya said: O Vidura, the four millenniums are called the Satya, Treta, Dvapara and Kali yugas. The aggregate number of years of all of these combined is equal to twelve thousand years of the demigods.