Performing a HEAD request to an artifact such as:
return a non conformant Last-Modified HTTP header date format which is not always GMT(https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Last-Modified).
This actually breaks some integrations that are not able to download such artifacts, apt-get for instance or puppet when using an http file resource.
The issue seems to be already solved in recent versions of Artifactory:
Steps to reproduce:
Observer how `last-modified` is not GMT(it might actually return a GMT date some times)