I notice that 1f2228c changed from hard to soft links citing NAR issues. Is that relevant here?

IIRC NARs don't preserve hardlinks, i.e. it's effectively as if you did a plain copy to most users, and the files being hardlinked will depend primarily on user's "optimising" their nix store. I don't know about any other issues.

Because of the symbolic posix link pointing to the local dir, the upstream software parses the contents of the zoneinfo directory multiple times because it follows symlinks and an error occurs because of this.

What software? What error?

What software? What error?

The standard library of the D programming language called Phobos.
I already patched it to not follow symlinks (see ThomasMader@6e15600#diff-9da5b94b5c73489302d04c387fbbf0c9R91) but wanted to make sure that tzdata has a standard layout before going upstream.
In Commit 1f2228c is mentioned though that other distributions are using symlinking too.
If that is true this PR can be closed.

Ubuntu is using symlinking, but without loops. This is better: e75d458

I've pushed my fix to staging. GitHub should close this issue when it reaches master.

@FRidh Thank you, I was considering doing this myself.

@orivej that was github; I merged staging into master.

@FRidh My bad, I did not expect staging to be merged to master so soon. But please, configure git with git config --global merge.ff false (and git config --global pull.rebase true), or at least use git merge --no-ff when merging staging into master, or it messes up the first-parent history and the history tree of the repository. (This effect was described here and here.) I have almost recovered the proper history in fbbda41.