Cavan Scott on the Ghoulactic Horrors of Tales from the Death Star on StarWars.com (backup link) states that the events of Star Wars Adventures: Tales from Vader's Castle take place around the time of the events of Rogue One: A Star Wars Story, which Star Wars: Timelines dates to 1 BBY. Timelines also dates the flashback events of Star Wars Adventures: Tales from Vader's Castle 4 to 1 BBY, therefore meaning Tales from Vader's Castle must occur in 1 BBY.
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