Paul W. answered 11/29/19
Dedicated to Achieving Student Success in History, Government, Culture
Like all Religions, the Hindu Faith evolved over many centuries. The fact that the ideas and practices that would become the Hindu Faith first appeared in the far distant past is compounded by the fact that, compared with other civilizations, only a very small amount of written sources for the early history of the Indian sub-continent have survived. Because of these factors, it's very doubtful if we will ever be able to point to a specific date and say "That's the day / year that the Hindu Faith began."
Again, like virtually all Religions, the foundation of the Hindu Faith was the religious beliefs that came before the Hindu Faith. This is because virtually all Religions incorporate ideas and practices from other, earlier Religions (as an example, Christianity incorporates features of Judaism, Islam incorporates features of Christianity). Historians have proposed that the formation, from a combination of earlier beliefs and practices, of the earliest form of the Hindu Faith likely took place over a period of eight centuries, roughly between 500 B.C./B,C.E. and 300 A.D./C.E. This period of 'fusion' is thought to have begun at the end of what is known as the Vedic Period (1500-500 B.C./B.C.E.) in the history if the Indian sub-continent.
By at least roughly 300 A.D./C.E. the basic features that identify the Hindu Faith were present, such as the belief in a near endless cycle of birth-death-rebirth, the concept of Karma, and the division of society into exclusive castes.