sandhyā - transitional period before; sandhyā-amśayoḥ - 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.

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.