This is about the only use case for local time that makes sense to me. But this is a UI issue, and it seems to me that that should be something that comes from a UI library or framework, not from libc and or /etc or environment variables.

(I’m using “UI” broadly. A user session on a UNIXy system could have an associated timezone, although such a design should allow changing the timezone without logging on and off. And this “10pm local” thing is quite different from an ordinary zoned time in that “10pm local in 10 days” does not correspond to an actual known UTC time because the local time zone may change.)