When do have archiving for a build, then the files on the master have the original timestamps of the file (same as on the slave).
But when you download it in a zip with '(all files in zip)' then the last modification date of file is the datetime of that moment, instead of original.

We have a job which archives a number of logfiles. Normally you can order it on datetime to get the last logfile, but when you download it in a zip ordering is impossible.