eta bhavi' kali-kale prathama sandhyaya
avatirna haila krsna apani nadiyaya
eta—thus; bhavi'-thinking; kali-kale—in the Age of Kali; prathama—first; sandhyaya—in the junction; avatirna haila—descended; krsna—Lord Krsna; apani—Himself; nadiyaya—in Nadia.
Thinking thus, the Personality of Godhead, Sri Krsna Himself, descended at Nadia early in the Age of Kali.
The prathama-sandhya is the beginning of the age. According to astronomical calculation, the age is divided into twelve parts. The first of these twelve divisions is known as the prathama-sandhya. The prathama-sandhya and sesa-sandhya, the last division of the preceding age, form the junction of the two ages. According to the Surya-siddhanta, the prathama-sandhya of Kali-yuga lasts 36,000 solar years. Lord Caitanya appeared in the prathama-sandhya after 4,586 solar years of Kali-yuga had passed.
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