यस्मादर्वाक्संवत्सरोऽहोभिः परिवर्त-ते ।तद्देवा ज्योतिषां ज्योतिरायुर्होपास-तेऽमृतम् ॥ १६ ॥
In plain words
The year turns through its days, yet never gets beyond this source. That is the light behind all lights — the gods themselves worship it as life itself, the deathless one.
Close to the Sanskrit
That from which the year, revolving with its days, does not reach beyond — that light of lights the gods indeed worship as life, the immortal.