Panini's own text carries no date and almost nothing external is known about his life, so his working century has to be inferred rather than read off a record, and the lines of evidence point in different directions. His grammar uses the words rupya and nishka for coined money, and numismatists date those coin types in India to the fourth century BCE; Johannes Houben has argued this places Panini at around 350 BCE on unrefuted concrete grounds. Hartmut Scharfe has argued instead that the language Panini's own grammar describes sits close enough to the language of the Upanishads and the Vedic sutras to suggest a fifth or sixth century BCE date, a linguistic argument that does not touch the coinage evidence directly. George Cardona, weighing both, holds that the evidence taken together supports a date no earlier than 400 BCE and that the case for anything earlier depends on interpretation rather than proof. MacTutor's own independent review of the question calls the proposed dates pure guesses and finds proposals spanning the fourth through the seventh century BCE. No consensus exists among these positions, and none has become the settled view.
What would resolve this A securely dated external reference to Panini himself, or to the Ashtadhyayi by name, from an inscription, a coin, or a text whose own date is independently fixed, would resolve it. Short of that, resolution would need either an agreed dating of the coin terminology Panini's grammar assumes that displaces or confirms the current fourth century BCE numismatic reading, or a linguistic dating method for Vedic-adjacent Sanskrit precise enough to be preferred over both the coinage evidence and rival linguistic readings. Absent new evidence of either kind, the dispute stays where the current scholarship leaves it: a disagreement over how to weigh evidence that is itself not in dispute.
OpenHistorical linguistics, Sanskrit philology and Indology, numismaticsPanini (MacTutor)