http://wiki.openvz.org/Updating_Ubuntu_template

Set the correct timezone, choosing the right value (mine is Europe/Rome):

dpkg-reconfigure tzdata

In this way we preserve future updates

This is an alternative old way

rm -rf /etc/localtime 2>/dev/null
unlink /etc/localtime 2>/dev/null
ln -s /usr/share/zoneinfo/Europe/Rome /etc/localtime