The earliest mention of the term Saura is in Vedic and Upanishadic texts of Hinduism. For example, it appears in chapter 7.2 of the Sankhayana Aranyaka embedded in the Rigveda, and in the Maitri Upanishad, in both it contextually means Surya. In the Mahabharata and the Puranas, the term is used to refer to the worshippers of sun deity. In esoteric Buddhism, the term appears in the context of yogi and deity, with alternate spelling of savara.
The solar day and months in the Vedic era calendars and in the medieval Indian calendars are prefaced as saura, to differentiate them from lunar system in the lunisolar calendars. However, the name of saura months in Vedic texts and medieval texts are different, with the medieval era linking it to the zodiac system that is same as and influenced by the Greek zodiac system. Timekeeping as well as the nature of solar and moon movements are mentioned in Vedic texts. For example, Kaushitaki Brahmana chapter 19.3 mentions the shift in the relative location of the sun towards north for 6 months, and south for 6 months.
A saura (Sanskrit: सौर) day is defined in medieval Hindu texts as the period during which the sun stays within one degree of an ecliptic arc. A saura month is defined in two ways. One, as the period in which the sun stays within one zodiac sign. Second, as the period of thirty intervals of sunrises.
A complete list of saura months of the Vedic era is found in the Yajurveda (~1000 BCE). It is so different from the names of ancient Persian/Avestan months, according to Louis Gray, that it "precludes any possibility of mutual influence" between their two calendar system.
The Vedic solar months were grouped into six by the names given to the months. The "sweet" months – Madhu and Madhava – corresponded to spring. The "bright" months to summer, the "cloudy" names to monsoons, the "sapful" nomenclature for autumn harvest, the "forceful" to winter, and the "ascetic" names – Tapas and Tapasya – reminding of two months of meditation and austere life. Both the Vedic saura month names and the zodiac-based month names are found in different chapters of the Bhagavata Purana. Its chapter 12.11, contains almost identical solar month names as the Yajurveda, with the exception of Sahasya which is named as Pusya. Further, the Bhagavata Purana links each Vedic solar month to one of the twelve Adityas.
Many scholars state that the sun (saura), moon (soma), planets, zodiac-based astrology systems now called Hindu astrology is a field that developed in the centuries after the arrival of Greek astrology with Alexander the Great, because their zodiac signs are nearly identical.