ADDITIONAL SYSTEM INFORMATION :
openjdk 23
windows, linux

A DESCRIPTION OF THE PROBLEM :
Currently the output of jar is non reproducible, for example

----
mkdir out; touch out/a
export SOURCE_DATE_EPOCH=1;jar --create --file classes.jar -C out .
touch out/a;
export SOURCE_DATE_EPOCH=1;jar --create --file classes2.jar -C out .
----

classes.jar and classes2.jar will differ.

It is possible to use --date with JDK 19 or newer but it is not supported by older versions of jar, at that point it might be easier to use strip-nondeterminism to support multiple environments.


https://reproducible-builds.org/docs/source-date-epoch/

Already explains why it is a good idea to support the environment variable (if the output of a command is not already reproducible).