That's exactly right. Here's what I had to add to my script to work:

use Date::Manip::Lang::english;
use Date::Manip::Lang::index;
use Date::Manip::Date;
use Date::Manip::Delta;
use Date::Manip::Recur;
use Date::Manip::Zones;
use Date::Manip::Obj;
use Date::Manip::TZ;
use Date::Manip::Base;
use Date::Manip::TZ::etgmt00;
use Date::Manip::TZ::amchic00;
Date_Init("tz=america/chicago");
[download]

Note the Date_Init() call at the end of that sequence which guarantees that my timezone alligns with the pulled in modules.

Thank you for your help!