The following commands will install the required software, and then find the best server to synchronize with.
apt-get install -y --force-yes ntp ntpdate /etc/init.d/ntp stop ntpdate -u 0.europe.pool.ntp.org ntpdate -u 0.europe.pool.ntp.org ntpdate -u 0.europe.pool.ntp.org /etc/init.d/ntp start ntpq -p
Example output:
root@debian7:~# ntpdate -u 0.europe.pool.ntp.org
14 May 11:11:13 ntpdate[37185]: step time server 87.117.247.137 offset 200343.474928 sec
root@debian7:~# ntpdate -u 0.europe.pool.ntp.org
14 May 11:11:23 ntpdate[37238]: adjust time server 5.9.40.108 offset 0.002920 sec
root@debian7:~# ntpdate -u 0.europe.pool.ntp.org
14 May 11:11:36 ntpdate[37239]: adjust time server 5.9.40.108 offset -0.001120 sec
root@debian7:~# /etc/init.d/ntp start
[ ok ] Starting NTP server: ntpd.
root@debian7:~# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
ntp.luna.nl 213.136.0.252 2 u 1 64 1 9.807 -3.671 0.391
textnews.news.c 94.228.220.14 3 u - 64 1 10.671 4.814 0.439
max.coevoet.nl 164.47.15.177 3 u 1 64 1 11.161 -2.069 0.000
livestatus.org 193.67.79.202 2 u - 64 1 10.258 -2.359 0.000