The Gemara Bava Basra 14b tells us that the recorded prophecies of twelve prophets were put together as one book to preserve them: the risk of seeing them lost if they were ‘cast’ as twelve small individual books was too great. They were bound together in one large scroll called the Trei Asar. The Trei Asar are: Hoshea, Yoel, Amos, Ovadiah, Yonah, Micha, Nachum, Chabakuk, Tzefania, Chaggai, Zecharia and Malachi. These are not Neviim who prophesied during the same period. Chaggai and Malachi lived during the final period of the Neviim, at the time of the second Beis Hamikdash (after the Purim story), and Chaggai was a member of the Anshei Kenesses Hagdolah who fixed our prayer texts. Yet Hoshea’s prophecy preceded that of Yeshaya (well before the destruction of the first Mikdash). Thus, our Trei Asar prophets span over 350 years – from the middle of the First Temple to the early years of the Second Temple.