Matsyapurana 142.37

142.37

kalpapramāṇo dviguṇo yathā bhavati saṃkhyayā
caturyugākhyā vyākhyātā kṛtaṃ tretāyugaṃ ca vai //

Now I shall give you the duration of a Manvantara in the Divine years It is 140,000(?) years in course of which the four ages come and go 71 times when one Manu takes the place of another At the completion of the Kalpa which is 14 times one Manvantara, the great dissolution of the world takes place which lasts for a period twice as much as one Kalpa The age of the four yugas has been thus described—32 37