To initially setup the time if there is a big difference you can use the following command

 /usr/sbin/ntpdate -s -b -p 8 -u yourISP.NTP.Server.IP

Debian:

Setting timezone:
sudo dpkg-reconfigure tzdata

/etc/ntp.conf
server 0.bg.pool.ntp.org
server 1.europe.pool.ntp.org
server 2.europe.pool.ntp.org

Great references http://www.akadia.com/services/ntp_synchronize.html

hwclock –systohc