Check your current timezone by just running

# date
Thu Mar 21 18:02:49 MST 2012

Or checking the timezone file at

# more /etc/timezone
US/Arizona

So to change it just run

$ sudo dpkg-reconfigure tzdata

And follow on screen instructions. Easy.

Also be sure to restart cron as it won’t pick up the timezone change and will still be running on UTC.

# /etc/init.d/cron stop
# /etc/init.d/cron start