New version available here: vedabase.io

SB 3.11.20

sandhyā-sandhyāṁśayor antar
 yaḥ kālaḥ śata-saṅkhyayoḥ
tam evāhur yugaṁ taj-jñā
 yatra dharmo vidhīyate
Synonyms: 
sandhyā — transitional period before; sandhyā-aṁśayoḥ — and transitional period after; antaḥ — within; yaḥ — that which; kālaḥ — duration of time; śata-saṅkhyayoḥ — hundreds of years; tam eva — that period; āhuḥ — they call; yugam — millennium; tat-jñāḥ — the expert astronomers; yatra — wherein; dharmaḥ — religion; vidhīyate — is performed.
Translation: 
The transitional periods before and after every millennium, which are a few hundred years as aforementioned, are known as yuga-sandhyās, or the conjunctions of two millenniums, according to the expert astronomers. In those periods all kinds of religious activities are performed.