To have the correct time and date in Linux is very important, a lot of things depends on it. It does not matter if you are using Linux to power your personal computer or you have a Linux server. The server and system clock needs to be on time.

Set date from the command line

date +%Y%m%d -s "20120418"

Set time from the command line

date +%T -s "11:14:00"

Set time and date from the command line

date -s "19 APR 2012 11:14:00"

Linux check date from command line

date

Will show you something like this:

Thu Apr 19 15:17:34 BOT 2012

Set hardware clock

The hardware clock is the clock that runs in you PC hardware even if you disconnect it from the main power supply. This is because it has a lithium battery in the modern computers and another type of battery in the old ones.

We'll see differences between hardware clock and system clock

hwclock --show

Will output something like this:

Thu 19 Apr 2012 03:23:05 PM BOT -0.785086 seconds

Now check the system clock

date

Will output something like this:

Thu Apr 19 15:26:41 BOT 2012

Let's set the hardware clock to local time:

hwclock --set --date="2012-04-19 16:45:05" --localtime

If you want to set it to UTC time use:

hwclock --set --date="2011-04-19 20:45:05" --utc

Set the timezone

To set the timezone of your system clock do the following:

cp /usr/share/zoneinfo/America/La_Paz /etc/localtime

Choose the right timezone for you.

Automatically adjust your computer clock

To have your system to automatically adjust time we need to install ntp. Get it from your repository. Once installed you can configure it this way:

Edit the file /etc/ntpd.conf. It will look like this:

# With the default settings below, ntpd will only synchronize your clock.

#

# For details, see:

# - the ntp.conf man page

# - http://support.ntp.org/bin/view/Support/GettingStarted

# - https://wiki.archlinux.org/index.php/Network_Time_Protocol_daemon

# Associate to public NTP pool servers; see http://www.pool.ntp.org/

server 0.pool.ntp.org

server 1.pool.ntp.org

server 2.pool.ntp.org

# Only allow read-only access from localhost

restrict default noquery nopeer

restrict 127.0.0.1

restrict ::1

# Location of drift and log files

driftfile /var/lib/ntp/ntp.drift

logfile /var/log/ntp.log

# NOTE: If you run dhcpcd and have lines like 'restrict' and 'fudge' appearing

# here, be sure to add '-Y -N' to the dhcpcd_ethX variables in /etc/conf.d/net

Be sure to start the daemon, and to make it start automatically when the system boots.

On Arch Linux is: /etc/rc.d/ntpd start on Debian and derivatives /etc/init.d/ntpd start

Update from the command line against a time server

You can update the clock manually, without the need of the daemon with ntpdate

ntpdate 129.6.15.28

You will get something like this:

19 Apr 15:45:23 ntpdate[10948]: step time server 129.6.15.28 offset -45.697084 sec