CC Ādi 3.7

satya, tretā, dvāpara, kali, cāri-yuga jāni
sei cāri-yuge divya eka-yuga māni
Word for word: 
satya — Satya; tretā — Tretā; dvāpara — Dvāpara; kali — Kali; cāri-yuga — four ages; jāni — we know; sei — these; cāri-yuge — in the four ages; divya — divine; eka-yuga — one age; māni — we consider.
Translation: 
We know that there are four ages [yugas], namely Satya, Tretā, Dvāpara and Kali. These four together constitute one divya-yuga.