sudo dpkg-reconfigure tzdata

# yum install ntp

# vi /etc/ntp.conf

#server pool.ntp.org

# /etc/init.d/ntpd start

# ntpdate pool.ntp.org

date --set="STRING"

# date -s "2 OCT 2006 18:00:00"

# date --set="2 OCT 2006 18:00:00"

# date +%Y%m%d -s "20081128"

# date +%T -s "10:13:13"

# date +%T%p -s "6:10:30AM"

# date +%T%p -s "12:10:30PM"

# just query
bash-4.2$ rdate pool.ntp.org
rdate: [pool.ntp.org]   Wed Jun 12 11:05:40 2013

# set system time
bash-4.2$ rdate -s pool.ntp.org

sudo ntpd -qg; sudo hwclock -w

sudo apt-get install ntp
sudo dpkg-reconfigure ntp
ntpq -p