While much of the timeline for older Legend of Zelda titles has been set in stone by the Hyrule Historia, Tears of the Kingdom and its predecessor hold a strange placement in the ongoing lore of Hyrule. It is already apparent that Breath of the Wild is at the end of the timeline, as time travel and changes to the established ancient past in this latest title appear to redefine that placement entirely.
After the release of Breath of the Wild and the lead-up to Zelda: Tears of the Kingdom, Nintendo has been increasingly cryptic about the current state of the Zelda timeline, only stating for a fact that this takes place at the current end. However, some of the references made within the newly discovered Depths beneath Hyrule and the focus of the story separate this new era of Zelda's timeline.
References in Hyrule's Depths
Unlike Zelda: Breath of the Wild with the majority of its referential gear being hidden across shrines and the later added EX chests, most of the equipment from the past like Ocarina of Time's armor set can be found in the depths. While this isn't the case for every single piece of armor or weapon that comes from the older series, a large amount of these items are found in the forgotten underground, in ancient Zonai chests. The implication here being that most of these gear sets aren't from Zelda: Tears of the Kingdom's personal past, but an even older past from before the initial founding of Hyrule.
Of course, references to older games aren't exactly the most iron-clad evidence of the canon, especially considering the way that both Zelda: Breath of the Wild and Tears of the Kingdom fail to commit to any of the three established timelines. Instead, this is more of a theme that Zelda: Tears of the Kingdom's armor sets follow when it relates to collecting stuff that makes reference back to the rest of the series. More importantly, it is the connection to the Depths, the Zonai, and the founding of Hyrule that makes finding gear from previous games down there specifically so impactful for the larger timeline.
Founding a Surface Hyrule
Another hint that the timeline in Tears of the Kingdom doesn't exactly line up with older games in the series is the events that take place in ancient Hyrule, specifically with the founding of the kingdom by King Rauru and Queen Sonia. Going back to the beginning of the previously established Zelda timeline, this already conflicts a bit with Skyward Sword, which had Hylians living on Skyloft before descending to the surface. It's an origin that could be hand-waved to show the Hylians heading back to Skyloft for a time before coming back down to the surface, but that doesn't appear to be the history of Zelda: Tears of the Kingdom's Sky Islands.
Even trying to stretch the history of Hyrule out, this still leaves an inconsistency in terms of Ganondorf and the original Demon King Demise, who hadn't been defeated and reincarnated until after the events of Skyward Sword. No matter how Tears of the Kingdom and Skyward Sword are compared, the narratives and lore do not match up with each other. So, the founding of Hyrule coming alongside the rise of Ganondorf as the Demon King appears to set a new continuity for the heroes and villains of the series.
Tears of the Kingdom is a Reset, Not a Continuation
All of these seeming contradictions between Tears of the Kingdom and the previous lore appear to present a new timeline, rather than a continuation of everything that had come before. Instead, a lot of the evidence appears to suggest that this new version of Ganondorf appearing at the founding of Hyrule and Zelda traveling back in time might have made a completely new split in the timeline. Additionally, other Legend of Zelda references suggest a separation that establishes past games as legends, suggesting Breath of the Wild is a new start that Tears of the Kingdom solidifies with its references and storytelling.
The Legend of Zelda: Tears of the Kingdom is available now for Switch.