The ancient Elvish week contained a day named Aldúya (or Orgaladhad in Sindarin) in reference to the Two Trees of Valinor. The Númenórean week retained that day, but renamed it Aldëa (or Orgaladh) in sole dedication to the White Tree Telperion, which they held in special reverence.

Ultimately the Númenórean system came to be used throughout the western lands of Middle-earth, though it is unclear whether their special dedication to Telperion was retained. In general use, the Quenya names were normally maintained, except in the Shire. The Shire-hobbits used a version of the name translated into an ancient form of the Common Speech, resulting in Trewesdei. As the centuries passed, this name would gradually change, so by the end of the Third Age, it was generally referred to by the Shire-hobbits as Trewsday.