SB 9.10.51

tretāyāṁ vartamānāyāṁ
 kālaḥ kṛta-samo ’bhavat
rāme rājani dharma-jñe
 sarva-bhūta-sukhāvahe
Synonyms: 
tretāyām — in the Tretā-yuga; vartamānāyām — although situated in that period; kālaḥ — the period; kṛta — with Satya-yuga; samaḥ — equal; abhavat — it so became; rāme — because of Lord Rāmacandra’s being present; rājani — as the ruling king; dharma-jñe — because He was fully religious; sarva-bhūta — of all living entities; sukha-āvahe — giving full happiness.
Translation: 
Lord Rāmacandra became King during Tretā-yuga, but because of His good government, the age was like Satya-yuga. Everyone was religious and completely happy.
Purport: 

Among the four yugas — Satya, Tretā, Dvāpara and Kali — the Kali-yuga is the worst, but if the process of varṇāśrama-dharma is introduced, even in this Age of Kali, the situation of Satya-yuga can be invoked. The Hare Kṛṣṇa movement, or Kṛṣṇa consciousness movement, is meant for this purpose.

kaler doṣa-nidhe rājann
 asti hy eko mahān guṇaḥ
kīrtanād eva kṛṣṇasya
 mukta-saṅgaḥ paraṁ vrajet

“My dear King, although Kali-yuga is full of faults, there is still one good quality about this age: simply by chanting the Hare Kṛṣṇa mahā-mantra, one can become free from material bondage and be promoted to the transcendental kingdom.” (Bhāg. 12.3.51) If people take to this saṅkīrtana movement of chanting Hare Kṛṣṇa, Hare Rāma, they will certainly be freed from the contamination of Kali-yuga, and the people of this age will be happy, as people were in Satya-yuga, the golden age. Anyone, anywhere, can easily take to this Hare Kṛṣṇa movement; one need only chant the Hare Kṛṣṇa mahā-mantra, observe the rules and regulations, and stay free from the contamination of sinful life. Even if one is sinful and cannot give up sinful life immediately, if he chants the Hare Kṛṣṇa mahā-mantra with devotion and faith he will certainly be freed from all sinful activities, and his life will be successful. Paraṁ vijayate śrī-kṛṣṇa-saṅkīrtanam. This is the blessing of Lord Rāmacandra, who has appeared in this Age of Kali as Lord Gaurasundara.