hindu astrology uses the concept of days under the regency of a planet under the term "vāsara", the days of the week being called "āditya-, soma-, maṅgala-, budha-, guru-, śukra-," and "śani-vāsara". "śukrá" is a name of venus (regarded as a son of bhṛgu); "guru" is here a title of bṛhaspati, and hence of jupiter; "budha" "mercury" is regarded as a son of "soma", i.e. the moon. knowledge of greek astrology existed since about the 2nd century bc, but references to the "vāsara" occur somewhat later, during the gupta period ("yājñavalkya smṛti", c. 3rd to 5th century), i.e. at roughly the same period the system was introduced in the roman empire.