Changing Timezone and setting date back on 5220 Appliance ..

Hi All, - setting back time on a unix platform have previously been a "handle with care" situation with gradually changing the time by decreasing or advancing the clock over longer time but I find my self in a situation where I need to change the timezone fro UTC to (US eastern Standar Time (UTC-5 hours) on a running 2.5.2 appliance unit ..

Have any on tryed this without complications ..and what are the steps involved ?

brgds

Søren