1. Job has to be about the age of his friends Eliphaz the Temanite, a descendant of Esau, and Bildad the Shuhite, possibly a descendant of Abraham’s youngest son Shuah. So he couldn’t have lived any earlier than Eliphaz the father of Teman, who quite possibly is the same as Job’s friend. That would put his birth at around 2220 AM, the earliest date suggested by the Babylonian Talmud. And it’s quite likely that he was a fairly close relative of both, being descended, like them, from Abraham—in his case, most likely through Keturah.
2. Job’s story picks up after his ten children are grown, which would put his age around sixty. He then lived another 140 years, and it was very uncommon for someone to live that long after Abraham’s time. And any time after Moses’ generation is completely unreasonable.
3. Although written in Hebrew, the text of Job contains several archaic words, references to ice age conditions, mention of a monetary unit current in Jacob’s day, and a total lack of any Levitical system of worship. All of these features support the early date for Job’s life, as well as an eyewitness source for the historical data in the book.
4. The references to Job’s enemies in chapter one are quite compatible with an early date, but not a late one.
5. The reference to iron in ch. 19 and ch. 28 drive evolutionists to a late date, as they don’t believe iron-working had yet evolved by the beginning of the second millennium BC. Those of us who have read the history of those times know otherwise, so the early date is not threatened. It doesn’t seem to have occurred to these people that the reason there isn’t any archeological iron in the early layers is that it has long since rusted away by now.
Now, this is the interesting thing: how did Moses find out about Job? Well, it’s quite possible that Job was one of his own ancestors. The final words of the book are to the effect that Job died after living to see his great-grandchildren. What if one of those was Moses?
To carry it just one step farther, Job had three daughters; his second cousin Levi had three sons. If Kohath the son of Levi had married any one of the daughters of Job, Amram would have been Job’s grandson, and Moses his great-grandson. Some of Moses’ second cousins would have been the great-grandsons whom Job lived to see. And it stands to reason that Moses’ grandmother would have brought with her as part of her dowry an account of her famous father, brought up to date as far as her adulthood. It only remained for Amram, when he acquired the document by inheritance, to bring it up to date with the death of his maternal grandfather, before making it available to his son Moses to have copied for his personal library.
"The daughters of Zelophehad speak right: thou shalt surely give them a possession of an inheritance among their father's brethren; and thou shalt cause the inheritance of their father to pass unto them. And thou shalt speak unto the children of Israel, saying, If a man die, and have no son, then ye shall cause his inheritance to pass unto his daughter. And if he have no daughter, then ye shall give his inheritance unto his brethren. And if he have no brethren, then ye shall give his inheritance unto his father's brethren. And if his father have no brethren, then ye shall give his inheritance unto his kinsman that is next to him of his family, and he shall possess it: and it shall be unto the children of Israel a statute of judgment, as the LORD commanded Moses." --Numbers 27:8-11
PS 'Ayoubian' is a fancy way of saying 'descended from Job.'