Can you force it to some time other than 0? Ex. I've seen some packages force timestamps to the git commit timestamp, which is nice but still fixed.

This is an approach you can use when building Docker images in Nix flakes: https://github.com/aksiksi/ncdmv/blob/aa108a1c1e2c14a13dfbc0...

The standard usually isn't 0s since epoch:

https://bugs.openjdk.org/browse/JDK-8264449 https://reproducible-builds.org/docs/source-date-epoch/

IME Erlang was like this ~8 years ago (the last time I touched it) but things may have changed since then.

What issues? I'm not aware of any Java build process that checks timestamps.

JARs are archives, and archives have timestamps.

You can remove those with some extra work.

Just add a post-process step that sets the output artifacts' timestamps (including its content)?

Wouldn't that work?

Yes, just add that.

Can you elaborate on the root causes?