Hindu scriptures are classified into two parts: Shruti ("śruti": what has been heard) and Smriti ("smṛti": what has been retained, remembered). The Vedas are classified under "śruti". A commonplace opinion in Southern Asian religious discourse suggests that, unlike other religions which claim the authority of their scriptures as being delivered by a personal God or special messengers of God, "Hindus" claim that the Vedas do not owe their authority to anybody; rather, the Vedas themselves are the authority, being identical with the eternal knowledge of God. This view, along with the classificatory schema, is a product of the Pūrva-Mīmāṁsā-darśana, one of the earliest hermeneutical schools in Indian antiquity. There is some evidence, however, that this school was not the only early opinion on the origins of the Veda. cf., the "Aitihāsikas" According to the Mīmāṃsā tradition, the mass of knowledge called the Veda became manifested to historical being via the divine mediation of persons called Rishis, the Seers. This mass of knowledge was eventually recorded in written form, though for the greater part of Indian history, these works were passed from generation to generation by a sophisticated practice of mnemonic heuristics, so that many thousands of hymns were committed to memory in a phonetically conservative form; The written forms of these hymns offer us little outward information about the original dates of discovery or composition. Thus, historians of Vedic texts are frequently left to making highly inferential arguments for the works by various subtle, indirect clues.
Timeline
The following list provides a somewhat common set of reconstructed dates for the terminus ante quem of Hindu texts, by title or genre. All dates here given ought to be regarded as roughly approximate, subject to further revision, and generally as relying for their validity on highly inferential methods and standards of evidence.