In Indian astronomy, yoga (also called nityayoga) is a period of time, of varying lengths, during which the sum of the nirayana longitudes of the Sun and the Moon increases by an amount of 13 degrees 20 minutes (or, equivalently, 800 minutes).
[2] S. B. Dikshit in his Bhāratīya Jyotiṣ Śāstra observes: "It is not known what planetary position in the sky is indicated by yoga, and it is useful only in astrology.
"[3] In Indian astrology, the term yoga has been used to indicate luni-solar distances and planetary situations, associations, and combinations.
The names of the 27 nitayoga are: Nityayoga or yoga has a prominent place in traditional Indian almanac known as Pañcāṅg.
However, the yoga-s entered the Pañcāṅg calculations only several centuries after the other four elements became parts of the Indian alamanac.
Khaṇḍakhādyaka, another treatise composed by Brahmagupta in c.665 CE has a couplet of verses referring to yoga.
[4] Robert Sewell's The Indian Calendar contains a section which explains in meticulous detail how the Yoga at sunrise on a day specified by a date in the Common Era can be determined.
The procedure also explains how to find how much time has elapsed at the moment of sunrise since the beginning of the Yoga.
Hence it has absolutely no connection whatsoever with any astronomical phenomena as the week has no definable relation to the motion of the moon or the sun.