yes, first you will need to setup the "Ip-network-map" for that location's IP's in use, then map these to an "ip-network-region", then on the "change location" form, you can define a location for Chicago, and specify the "offset", in + or - hours from your main switch, then on you IP-Network-Region form, you can specify this "location", and if you did everything correctly, your phones will "map" to this region/location and have the correct time. as a bonus, you could also setup your own ARS for that location, if you happen to put out a media gateway with dialtone for that location..
mitch
AVAYA Certified Specialist