Nintendo has revealed The Legend of Zelda: Echoes of Wisdom's official place on the Zelda timeline, and it turns out that the princess's adventure happens directly before the events of the first game.
The Zelda timeline is, frankly, rather confusing – there's a whole timeline split after the events of Ocarina of Time depending on whether or not Link is defeated, so certain games only fit into the equation in one of these realities.
Echoes of Wisdom, it turns out, is one of these. As spotted on ResetEra, the official Japanese Zelda history page has now been updated to include the series' latest 2D romp, and it turns out that it's part of the 'Hero is Defeated' branch.
Specifically, it's sandwiched between The Legend of Zelda: Tri Force Heroes (the co-op-focused 3DS game) and The Legend of Zelda (the first one), although it's also worth noting that the "Decline of Hyrule Kingdom" is slotted in directly after Zelda's own adventure.
The timeline doesn't explain how many years each of the games are separated by, which could help explain a plot discrepancy some have pointed out on ResetEra which – without getting into spoilers – relates to the knowledge (or lack thereof) of the Triforce in the games in question.