Charles Ellicott Commentary Deuteronomy 31:29

"For I know that after my death ye will utterly corrupt yourselves, and turn aside from the way which I have commanded you; and evil will befall you in the latter days; because ye will do that which is evil in the sight of Jehovah, to provoke him to anger through the work of your hands." — Deuteronomy 31:29 (ASV)

In the latter days. —A not uncommon prophetic expression, used with some considerable latitude. It occurs for the first time in Genesis 49:1. (See also Numbers 24:14 and Deuteronomy 4:30.) Some would refer it to the “days of the Messiah,” and make it almost a technical term. But a comparison of these few passages will show that it cannot be tied strictly to any one period.