A procedure like reset-gzip-timestamp should be useful for
reproducibility purposes, adapted to zip based archives as Smalltalk's
STAR or Java's JAR binary formats, as some or all of their contents are
generated usually at build time.
On the latest Zip specification, which only seem to be encumbered
regarding encryption, there is one header ID which could be used for
timestamp purposes (0x0020) but third party header IDs are allowed,
which include a "commonly used" 0x5455 timestamp.