maven-jar-plugin datetime property

[delanym]

The format of https://maven.apache.org/plugins/maven-jar-plugin/jar-mojo.html#outputTimestamp
can be ISO 8601 or secs since epoch.

I need this to support https://maven.apache.org/guides/mini/guide-reproducible-builds.html#how-do-i-configure-my-maven-build

[delanym]

It would also be great to have the "commit date" in this format https://stackoverflow.com/questions/11856983/why-git-authordate-is-different-from-commitdate

Im not sure which one I'd eventually use.

[pascalgn]

I think this is something that could be added. Do you want to provide a PR for it?