His book was accepted early as part of the sacred literature: Ben-Sira (c. 180 B.C.) mentions him along with Isaiah and Jeremiah (Ecclus.
The wisdom of Jesus ben Sira (Sirach) is contained in the book commonly called Ecclesiasticus.
By about the beginning of our era the Jews had given up Hebrew and wrote in Aramaic; the process of expulsion had been going on, doubtless, for some time; but comparison with the later extant literature (Chronicles, the Hebrew Ecclesiasticus or Ben-Sira, Esther) makes it improbable that such Hebrew as that of Koheleth would have been written earlier than the 2nd century B.C. (for details see Driver's Introduction).
So also the coincidences of thought with Ben-Sira (Ecclesiasticus) are not decisive: cf.
In any case, since Ben-Sira belongs to about 180 B.C., the date of' Koheleth, so far as these coincidences indicate it, would not be far from 200 B.C. The contrast made in x.