SB 3.11.14

saṁvatsaraḥ parivatsara
 iḍā-vatsara eva ca
anuvatsaro vatsaraś ca
 viduraivaṁ prabhāṣyate
Synonyms: 
saṁvatsaraḥ — orbit of the sun; parivatsaraḥ — circumambulation of Bṛhaspati; iḍā-vatsaraḥ — orbit of the stars; eva — as they are; ca — also; anuvatsaraḥ — orbit of the moon; vatsaraḥ — one calendar year; ca — also; vidura — O Vidura; evam — thus; prabhāṣyate — they are so told.
Translation: 
There are five different names for the orbits of the sun, moon, stars and luminaries in the firmament, and they each have their own saṁvatsara.
Purport: 

The subject matters of physics, chemistry, mathematics, astronomy, time and space dealt with in the above verses of Śrīmad-Bhāgavatam are certainly very interesting to students of the particular subject, but as far as we are concerned, we cannot explain them very thoroughly in terms of technical knowledge. The subject is summarized by the statement that above all the different branches of knowledge is the supreme control of kāla, the plenary representation of the Supreme Personality of Godhead. Nothing exists without Him, and therefore everything, however wonderful it may appear to our meager knowledge, is but the work of the magical wand of the Supreme Lord. As far as time is concerned, we beg to subjoin herewith a table of timings in terms of the modern clock.

One truṭi — 8/13,500 second

One vedha — 8/135 second

One lava — 8/45 second

One nimeṣa — 8/15 second

One kṣaṇa — 8/5 second

One kāṣṭhā — 8 seconds

One laghu — 2 minutes

One daṇḍa — 30 minutes

One prahara — 3 hours

One day — 12 hours

One night — 12 hours

One pakṣa — 15 days

Two pakṣas comprise one month, and twelve months comprise one calendar year, or one full orbit of the sun. A human being is expected to live up to one hundred years. That is the way of the controlling measure of eternal time.

The Brahma-saṁhitā (5.52) affirms this control in this way:

yac-cakṣur eṣa savitā sakala-grahāṇāṁ
 rājā samasta-sura-mūrtir aśeṣa-tejāḥ
yasyājñayā bhramati saṁbhṛta-kāla-cakro
 govindam ādi-puruṣaṁ tam ahaṁ bhajāmi

“I worship Govinda, the primeval Lord, the Supreme Personality of Godhead, under whose control even the sun, which is considered to be the eye of the Lord, rotates within the fixed orbit of eternal time. The sun is the king of all planetary systems and has unlimited potency in heat and light.”