Apparently neither gpg nor gpgtar are currently capable of retaining a files's modification date upon decryption/extraction, at least not on Windows XP.

From what I can tell, gpgtar can correctly store said information which thing can be easily corroborated through --list-archive, but as far as gpg.exe goes, chances are it's not even storing it at all, and that's probably a more complicated issue relating directly to OpenPGP format itself.

If that much could done for at least the encrypted tar's, it would allow users to do away with third party applications such as 7-zip in cases where the preservation of timestamps is not optional.

Thanks for your time and sorry for any inconvenience.