The poem, "The Road Not Taken" was first published in 1916 in Robert Frost's book "Mountain Interval". The internal evidence in the poem seems to suggest that the seemingly casual and inconsequential choice he is forced to make in the poem is really likely to have been crucial—one of the choices of life that involve commitment or lead to the necessity of other choices that will divert the traveler forever from his original destination. His choice, in any event, “has made all the difference.”
Since that decision "has made all the difference", enough time seems to have elapsed for Frost to see the consequences of his choise.Thus, it seems to involve a choice that was made several years earlier, perhaps even when he was a young man. That period of time could be as early as 1892 when Frost graduated from high school as class poet and valedictorian or as late as 1915, a few years before the poem was published. Most likely, as with many poets, Frost started to write the poem and then took quite a bit of time polishing and refining it.