The timeline for this entry shows the period when the story of Aldarion and Erendis is set. The story itself must (of course) have been written at some point after II 985, though precise details of its dating are unknown.

It seems that the original tale of Aldarion and Erendis was created in Númenor itself. Most Númenórean literature was lost in the Downfall, but we're told that this particular story was preserved by Elendil, who found it of particular interest.

There is a point of confusion, however, arising from a reference within the story itself. One passage describes Aldarion sailing into the Bay of Belfalas, where he sees '...the mountains of the country of Amroth where the Nandor Elves still dwell' (Unfinished Tales Part Two II, Aldarion and Erendis). This must be a reference to the place that would later be called Dol Amroth, where the Nandor maintained a haven at a place named Edhellond. In his commentary to this account, Christopher Tolkien suggests that this implies authorship in Gondor at some point in the Third Age before III 1981 (when Edhellond was abandoned). Since we're elsewhere told that the original story came from Númenor, this must be an interpolation by a later Gondorian author. So, the extant version of Aldarion and Erendis apparently contains at least some changes - if only this single sentence - made by an unknown Gondorian long after its original composition.

To confuse matters even further, the name Amroth wasn't applied to this region until after the last ship had sailed from its haven (the ship from which the Elf-lord Amroth leapt to his doom) in III 1981. So, in theory, there was never a time when the 'country of Amroth' was both so named, and also occupied by Nandorin Elves. This is perhaps a translation convention; we might take it that the Gondorian editor or translator actually used some other name for the country of Amroth but, in the course of later editing or translation, the more familiar association with Amroth found its way into the text.