Had some problems with ntpdate on my debian virtual server .
Setting the time with ntpdate actually did not work. I am using debian etch 64bit.
I found this article usefull .
After running these commands
# set independent_wallclock
# echo 1 > /proc/sys/xen/independent_wallclock
I was able to set the time with
 ntpdate  0.europe.pool.ntp.org

set independent_wallclock
echo 1 > /proc/sys/xen/independent_wallclock
ntpdate  0.europe.pool.ntp.org