Apart from Jaina studies, Jacobi was interested in
Indian mathematics,
astrology and the
natural sciences, and using astronomical information available in the
Vedas, he tried to establish the date of their composition. Like
Alexander Cunningham before him he tried to systematise how, from the evidence available in inscriptions, a true local time could be arrived at. Jacobi's studies in astronomy have regained importance today in the context of the
Out of India theory, because his calculations led him to believe that the hymns of the
Rigveda were to be dated as early as 4500 B.C. Thus he is the only renowned Western Indologist whose research supports the claim of the proponents of the theory that the Vedas are to be dated back much earlier than the first half of the second millennium B.C. According to mainstream Indology, the
Indo-Aryan Migration took place during this period of time and the Vedas were only composed after the migration. When Jacobi published his views in an article on the origin of Vedic culture in the
Journal of the Royal Asiatic Society (1908), he therefore triggered a major controversy in Indology. In his later life, Jacobi focused on poetry, epics, and philosophy, particularly the school of
Nyaya-Vaisheshika. ==Honors==