This just runs ntpdate on your server.
You must run this with "--privileged" for it to be able to update the time.
Pretty much made this to run on boot2docker
docker run --privileged --rm cpuguy83/ntpdate
Pass in a custom server as such
docker run --rm --privileged cpuguy83/ntpdate 0.us.pool.ntp.org
Default is "0.pool.ntp.org"