References in the The Lord of the Rings seem to place the beginning of the Dominion of Men squarely at the end of the Third Age and the beginning of the Fourth. For example, Gandalf's words quoted above (spoken after the War of the Ring) strongly suggest that the Dominion had just begun, or was about to do so.

Other references, however, suggest that the emergence of the Dominion of Men was a more incremental process, and that it came into being gradually during the Third Age until it reached its culmination at the beginning of the Fourth. For example, in The Nature of Middle-earth (Part One IV, Time-scales) a discussion of the growing weariness of the Elves in Middle-earth describes it as '...increasing rapidly during the Third Age when the Dominion of Men was finally achieved.'