There are several ways of update date and time in linux , among which the simplest are:

For server

Easier however, there is the need to have internet connection, and ntpdate installed.

If you do not have ntpdate installed you can install from source: http://www.ntp.org/downloads.html , or whether you have the aptitude:

 aptitude install ntpdate 

You can find a list of servers ntp's the link: http://support.ntp.org/bin/view/Servers/NTPPoolServers

 ntpdate pool.ntp.org 

Logical disjunction

 ntpdate-u ntp.usp.br 

also can use the ip national observatory :

 ntpdate-u 200.20.186.75 

We can also put the script in cron to be checked hourly.

 crontab-e 

and put the code:

 00 **** ntpdate-u pool.ntp.org 

For the date command

This update can separate the date and time

Updating data

date-s 'yyyymmdd'

yyyy : the 4-digit year

mm : the 2-digit month

dd : the 2-digit day

Updating time

date-s 'hh: mm: ss'

hh : time from 00 to 23

mm : the 2-digit minute 00-59

ss : seconds with 2 digits 00-59