In answer to a reader’s question about the chronology of Solomon’s writings in the OT, I suggested this:

1. Proverbs is instruction to a son during his boyhood/adolescence/young adulthood.  That seems to put it early-ish in Solomon’s life.  He became king around 30 (there’s a complicated argument for this), and reigned 40 years (1 Kings 11:41).  Rehoboam became king at 41 (1 Kings 14:21),so he was born the year before Solomon’s accession.  He would have been 5 in Solomon’s fourth year when he began the temple and Solomon would have been 34 (1 Kings 6:1) and 12 when Solomon finished the temple in the 11th year of his reign when Solomon was 39 (1 Kings 6:37-38).  If Solomon is writing Proverbs during Rehoboam’s adolescence/young adulthood, he would have been writing it during his 40s.

2. Ecclesiastes is mature reflection on Solomon’s achievements as king.  It comes after he has built his own house and pleasure gardens and enjoyed the pleasures of women (Ecclesiastes 2), and has had time to find that it is all vanity.  Solomon took 13 years to complete his own house (1 Kings 7:1); we’re not giving a starting date as far as I can see, but it seems to have started after the temple was finished (cf. 6:37-38).  If that’s true, he started building his own house around the age of 40 and completed it in his early 50s.  He gathered women throughout his reign, but 1 Kings 11 emphasizes that he was turned from Yahweh during his old age.  If he completed his house at 53 or so, had enjoyed the pleasures of women, then his later reflections on the vaporousness of it all would reasonably happen during his late 50s/early 60s.  Which puts Ecclesiastes a decade or two after Proverbs.

3. The Song is a celebration of a unique love (SoS 6:9).  It seems that Solomon already has concubines and other wives, but not as many as he later gathers (6:8).  But he still desires one particular woman.  If this isn’t just cynicism, it seems as if the Song has to come early, before he is turned away to love many foreign women (1 Kings 11).  If, as many suggest, the Song is a celebration of his love for the daughter of Pharaoh, it would have been composed sometime early in his reign.