"You need to add a number of servers to the server
list. The Debian default is pool.ntp.org which works but isn't
always amazingly accurate because it makes no attempt to use time
servers near you. If you want more accuracy use the time servers
either on your continent (for instance europe.pool.ntp.org) or your
country (for instance uk.pool.ntp.org) one of your local country
servers.The optimal number of servers to listen to is three but two
will also give a good accuracy. If your ISP runs a time server for
you it is worth including it in your server list as it will often
be more accurate than the pooled servers and will help keep the
load down on the pool."
