The Hebrew scriptural canon was sealed at the end of the Babylonian Exile by the Anshei Knesset Hagedolah (Great Synod), around 450 B.C.
The above statement, of course, would be according to non Christian sources.
Critical opinion as to date ranged from c. 165 B.C. to the middle of the second century of our era (Wildeboer). The Catholic scholars Jahn, Movers, Nickes, Danko, Haneberg, Aicher, without sharing all the views of the advanced exegetes, regard the Hebrew Hagiographa as not definitely settled till after Christ. It is an incontestable fact that the sacredness of certain parts of the Palestinian Bible (Esther, Ecclesiastes, Canticle of Canticles) was disputed by some rabbis as late as the second century of the Christian Era (Mishna, Yadaim, III, 5; Babylonian Talmud, Megilla, fol. 7). However differing as to dates, the critics are assured that the distinction between the Hagiographa and the Prophetic Canon was one essentially chronological. It was because the Prophets already formed a sealed collection that Ruth, Lamentations, and Daniel, though naturally belonging to it, could not gain entrance, but had to take their place with the last-formed division, the Kéthubim.