When did Solomon write the Proverbs?

Answer 1

The Book of Proverbs was written over a fairly extended period by several different authors. The earliest material is about the spirit/goddess called Wisdom*, who did not enter the Jewish belief system until worship of the goddess Asherah had ceased among the Jews. This places the earliest layer of Proverbs no earlier than the Babylonian Exile, in the sixth century BCE. Although it was apparently not possible to remove material about Lady Wisdom, material was subsequently added to change the focus of the book away from Wisdom towards the concept of philosophical wisdom, incorporating the suggestion that perhaps this material, and the book as a whole, was really written much earlier, by King Solomon. Much internal evidence demonstrates that the Book of Proverbs was written in the second half of the first millennium BCE.

Footnote
* See for example Proverbs 1:20-33: "Wisdom crieth without; she uttereth her voice in the streets: She crieth in the chief place of concourse, in the openings of the gates: in the city she uttereth her words, saying, How long, ye simple ones, will ye love simplicity? and the scorners delight in their scorning, and fools hate knowledge? Turn you at my reproof: behold, I will pour out my spirit unto you, I will make known my words unto you. Because I have called, and ye refused; I have stretched out my hand, and no man regarded; But ye have set at nought all my counsel, and would none of my reproof: I also will laugh at your calamity; I will mock when your fear cometh; When your fear cometh as desolation, and your destruction cometh as a whirlwind; when distress and anguish cometh upon you. Then shall they call upon me, but I will not answer; they shall seek me early, but they shall not find me: For that they hated knowledge, and did not choose the fear of the LORD: They would none of my counsel: they despised all my reproof. Therefore shall they eat of the fruit of their own way, and be filled with their own devices. For the turning away of the simple shall slay them, and the prosperity of fools shall destroy them. But whoso hearkeneth unto me shall dwell safely, and shall be quiet from fear of evil."

Answer 2

Solomon wrote the Proverbs in the tenth century BC, before 931BC.