Following the initial settlement that took place in 36,453 BBY, a secondary migration occurred over a millennium later.
Dating notation using TYA was first revealed by the Star Wars Books Facebook page however it was not until Amazon.com previews of Dawn of the Jedi: Into the Void were released that it was revealed the acronym "TYA" represented "Tho Yor Arrival". Into the Void mistakenly placed the TYA date at 36,463 BBY.