Did you

    sudo service ntp stop
    sudo ntpd -gq
    sudo service ntp start

? (as already pointed out [here][1].)

Output should look like this:

    [ ok ] Stopping NTP server: ntpd.
    ntpd: time slew +0.001411s
    [ ok ] Starting NTP server: ntpd.

Note that it can be slow:

    time ntpd -gq
    ntpd: time slew -0.007043s
    
    real	0m7.063s
    user	0m0.040s
    sys	0m0.020s

You can also double check you are not talking to nothing;

    grep -P "^server" /etc/ntp.conf 
    server 0.debian.pool.ntp.org iburst
    server 1.debian.pool.ntp.org iburst
    server 2.debian.pool.ntp.org iburst
    server 3.debian.pool.ntp.org iburst
    ping -c 1 0.debian.pool.ntp.org
    PING 0.debian.pool.ntp.org (192.99.10.37) 56(84) bytes of data.
    64 bytes from sexi.fawong.com (192.99.10.37): icmp_req=1 ttl=55 time=32.8 ms
    
    --- 0.debian.pool.ntp.org ping statistics ---
    1 packets transmitted, 1 received, 0% packet loss, time 0ms
    rtt min/avg/max/mdev = 32.890/32.890/32.890/0.000 ms


  [1]: https://askubuntu.com/questions/254826/how-to-force-a-clock-update-using-ntp