Tolkien scholar Tom Shippey, who is supervising the show’s development, told German fansite Deutsche Tolkien that the estate has refused to allow the series to be set during any period other than the Second Age of Middle-earth.One advantage of having the series take place during the Second Age (noted by Shippey in the article) is that it gives the writers more room to develop stories and characters than they would have if the series were to take place during the later part of the Third Age (the time of The Hobbit and The Lord of the Rings) or the First Age (the time of The Silmarillion). In contrast to the First and Third Ages, Tolkien’s writings on the Second Age primarily are timelines and overviews of key historical events. However, the series—thankfully!—will be constrained by the events that Tolkien did note (so the series, Shippey notes, “must not contradict anything which Tolkien did say”).
Spanning 3,441 years, the Second Age begins after the banishment of the dark lord Morgoth and ends with the first demise of Sauron, Morgoth’s servant and the primary villain in The Lord of the Rings, at the hands of an alliance of elves and men.
This is perhaps the best combination: a set of fixed events ensuring that the series can ‘stick the landing’ (the first defeat of Sauron in the Last Alliance would be a great way to end the series) while allowing genuine ‘creative room’ for the writing team.
So I remain cautiously optimistic about this…
(The linked article’s headline is rather misleading, I should note, as it seems to ignore the plethora of ‘plots’ throughout Tolkien’s many writings on Middle-earth. Moreover, if the series is set during the Second Age, it is ridiculously incorrect to claim that it’s an adaptation of The Lord of the Rings.)