From the introduction in the RSV: “The ancient folktale of a patient Job circulated orally among oriental sages in the second millennium B.C. and was probably written down in Hebrew at the time of David and Solomon or a century later (about 1000-800 B.C.). An anonymous poet of the Exile sixth century B.C. used it as a setting for the discussion between an impatient Job and his three friends and the Lord’s discourses from the whirlwind. A later poet contributed Elihu’s speeches.”
From the Catholic Encyclopedia: "(b) Age in which Job lived
According to the usual and well-founded assumption, Job lived long before Moses. This is shown by the great age he attained. He was no longer young when overtaken by his great misfortune (xii, 12; xxx, 1); after his restoration he lived one hundred and forty years longer (xlii, 16). His wealth like that of the Patriarchs, consisted largely in flocks and herds (i, 3; xlii, 12). The kesitah or piece of money mentioned in xlii, 11, belongs to patriarchal times; the only other places in which the expression occurs are Gen., xxxiii, 19, and Jos., xxiv, 32. The musical instruments referred to (xxi, 12; xxx, 31) are only those mentioned in Genesis (Gen. iv, 21; xxxi, 27): organ, harp, and timbrel. Job himself offers sacrifice as the father of the family (i, 5), as was also the custom of the Patriarchs. An actual offering for sin in the Mosaic sense he was not acquainted with; the holocaust took its place (i, 5; xlii, 8)."
newadvent.org/cathen/08413a.htm
Also from the Catholic Encyclopedia: “XI. TIME OF COMPOSITION
The author of the book is unknown, neither can the period in which it was written be exactly determined. Many considered the book the work of Job himself or Moses. It is now universally and correctly held that the book is not earlier than the reign of Solomon. On the other hand it is earlier than Ezechiel (Ezekiel 14:1-20). For it is the natural supposition that the latter gained his knowledge of Job from the Book of Job, and not from other, vanished, sources. It is claimed that allusions to Job have also been found in Isaias, Amos, Lamentations, some of the Psalms, and especially Jeremias. Many Catholic investigators even at the present time assign the book to the reign of Solomon; the masterly poetic form points to this brilliant period of Hebrew poetry. The proofs, however, are not very convincing. Others, especially Protestant investigators, assign the work to the period after Solomon. They support this position largely upon religious historical considerations which do not appear to have much force.”
newadvent.org/cathen/08413a.htm