I think it’s happening when I suspend a new user through the moderation queue. I reject the post and suspend them at the same time, and then the job ends up going into Sidekick with the “in 1000 years” text.
Is this a bug, or possibly a problem with my specific installation of Discourse?
The default suspension time for “permanent” is 1000 years, so I believe this is intended. You can see this by clicking “Suspend” on another user and checking the options, the forever button will likely say October 23, 3026 next to it.
Personally, it makes more sense to just not schedule a job to begin with, but it does the job at least.