Timestamp of files through ftp are different that actual timestamp

Proftpd might be doing a timestamp offset on your system.

Edit your /etc/proftpd.conf file, and add:

TimesGMT off
to the top of the proftpd.conf file. Save, exit, and restart proftpd.

Some reports mention to add the following code into the top section of your proftpd boot script:

export TZ=":/etc/localtime"
eg: /etc/init.d/proftpd or /usr/local/etc/rc.d/proftpd.

Reference:
http://bugs.proftpd.org/show_bug.cgi?id=2717
claims to have been fixed in 1.3.0rc5, so use 1.3.0 or higher.

Another report of modifying some code in mod_auth.c and recompiling (no followup on this yet)