How do I set time and date from the Internet?

Question

How do I retrieve the date from the Internet and set my computer's clock, from the command line?

Answer 1

A small command I found to update your time in case you don't want to install anything just to update the date. :)

sudo date -s "$(wget --method=HEAD -qSO- --max-redirect=0 google.com 2>&1 | sed -n 's/^ *Date: *//p')"

You can check whether date correctly understands the string before actually setting the time by running

$ date -d "$(wget --method=HEAD -qSO- --max-redirect=0 google.com 2>&1 | sed -n 's/^ *Date: *//p')"
Mon Jan 10 11:40:46 AM CET 2022

The wget command may be replaced by curl -Is --max-redirs 0 google.com.

Note that --method=HEAD is used because it seems that GET responses may be cached (with an old Date header) while HEAD responses are fresh.

Answer 2

Firstly, if you want to change your timezone you can use:

sudo dpkg-reconfigure tzdata

To update the time and date from the internet on a Linux distribution that uses a modern version of systemd, you can use:

timedatectl set-ntp true

Alternatively, you can install the reference NTP implementation as described below.

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Reference NTP implementation

Install

If ntpd is not installed use one of the following command to install ntpd:

• For RPM based:

  yum install ntp 
  

• For Debian based:

  sudo apt-get install ntp
  

Configuration

You should at least set following parameter in /etc/ntp.conf config file:

server <Time Server Name or IP Address>

For example, open /etc/ntp.conf file using vi text editor:

# vi /etc/ntp.conf

Locate server parameter and set it as follows:

server pool.ntp.org

Save the file and restart the ntpd service:

# /etc/init.d/ntpd start

You can synchronize the system clock to an NTP server immediately with following command:

# ntpdate pool.ntp.org

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Manually setting the date

For setting the time and date manually use the following syntax:

date --set="STRING"

For example, to set the date to 2 Oct 2006 18:00:00, type the following command as root user:

# date -s "2 OCT 2006 18:00:00"

OR

# date --set="2 OCT 2006 18:00:00"

You can also simplify format using following syntax:

# date +%Y%m%d -s "20081128"

To set time use the following syntax:

# date +%T -s "10:13:13"

where:

• 10: Hour (hh)
• 13: Minute (mm)
• 13: Second (ss)

You can use %p for the locale's equivalent of AM/PM:

# date +%T%p -s "6:10:30AM"
# date +%T%p -s "12:10:30PM"

Answer 3

I use this:

sudo ntpd -qg; sudo hwclock -w

first tell ntpd to just set the time and stop after that with -q. Also, in case a your clock has a big error we need to tell ntpd to also adjust in that case with -g. Finally write the clock to hardware to preserve the changes when rebooting with hwclock -w (-w for setting hardwareclock to current system time, there is a difference).

Answer 4

Some distributions are shipping rdate for that purpose. Basic usage:

# just query
bash-4.2$ rdate time.nist.gov
rdate: [time.nist.gov]   Wed Jun 12 11:05:40 2013

# set system time
bash-4.2$ rdate -s time.nist.gov

Answer 5

Use ntpdate, ntpd, or Chrony to connect to a NTP server.

Answer 6

After some research, I ended up with this. I also applied it to my own server:

sudo apt-get install ntp
sudo dpkg-reconfigure ntp
ntpq -p

If the last command shows a valid list of servers, you are good to go. The command will run a quite complex set of algorithms which will iterate your clock drift, among other things, and compensate for them. You will end up with a pretty accurate clock even if you lose the connection to the NTP servers. However, the command does require a few minutes to get started.

Source: here and here.

Answer 7

To find "peers" (hosts you can query) you can use ntpq -p.

If you already have an NTP service running you have to stop it before manually updating, for example using sudo service ntp stop.

Now you can query a peer, for example using sudo ntpdate "peer".

Answer 8

I also was looking for a non ntp/ntpd way of resetting clock periodically. I liked the google.com header parsing but found it did not work on ubuntu. I think this will also work on a Raspberry Pi.

sudo date +"%d %b %Y %T %Z" -s "$(wget -qSO- --max-redirect=0 http://google.com 2>&1 | grep '^  Date:' | cut -d' ' -f 5-)"

Also an alternative using curl instead of wget.

sudo date +"%d %b %Y %T %Z" -s "$(curl -s --head http://google.com | grep '^Date:' | cut -d' ' -f 3-)"

Tested on PI with Cellular Network and results are similar:

Using host & wget -- RCV: 1324 bytes SND: 581 bytes
Using host & curl -- RCV: 1318 bytes SND: 567 bytes

Note I use host to resolve google.com to an IP address so I can open only that IP for duration of this command with iptables.

Answer 9

Using rdate tool as suggested in manatwork's answer, but with SNTP protocol -n and IPv4 -4 options on:

# just print synced time, not set
rdate -n -4 -p time-a.nist.gov

# print and set synced time
sudo rdate -n -4 time-a.nist.gov

The tool may be installed on Debian this way:

sudo apt-get install rdate

Answer 10

If you are on Ubuntu or Ubuntu-derivative such as Mint, it implements

timesyncd in place of NTP.

You can check whether your timesyncd is set up correctly by running systemctl status systemd-timesyncd.

If you do not get something like

● systemd-timesyncd.service - Network Time Synchronization
 Loaded: loaded (/lib/systemd/system/systemd-timesyncd.service; enabled; vendor preset: enabled)
 Active: active (running) since Sun 2024-08-11 05:57:47 MSK; 46s ago

Then you my want to do something like the following:

$ sudo -i
# apt install systemd-timesyncd # You might have uninstalled it by mistake
# vi /etc/systemd/timesyncd.conf # add a line NTP=ntp.ubuntu.com, say
# systemctl restart systemd-timesyncd
# timedatectl set-ntp true
# systemctl status systemd-timesyncd # check that it works

Experts will improve my preliminary answer, hopefully