Which time server is used by Ubuntu?

Your system will use Ubuntu's NTP server at ntp.ubuntu.com by default.

To find what NTP server is being used, run:

grep ^server /etc/ntp.conf

If you get an error, then NTP is not installed. To install it, just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command(s) below:

sudo apt-get install ntp

Usually, ntp.ubuntu.com. This is supported by example preseed files and the value used by the server and network installation methods (for which, the debug output shows ntp.ubuntu.com as the value for the NTP server). To check the server status and time, you can run ntpdate in debug mode (to see if there are other problems), or in query mode (to just see the time):

ntpdate -d ntp.ubuntu.com # Debug mode
ntpdate -q ntp.ubuntu.com # Query mode