In attempting to the put the Minor Prophets in chronological order, dating Joel’s prophecy is one of the bigger challenges. Other prophets leave unambiguous internal evidence that help us date what they wrote; like, for example, dropping the name of a specific king, or mentioning the fall of Nineveh (which we can date to 612 B.C. from secular history) as either historical or else still future.
Joel doesn’t do that, at least not in any way most scholars deem conclusive.