An atomic clock is an expensive and bulky device. It is much more convenient to receive accurate time signals by phone, radio or satellite. Recently, the Internet has become another channel for obtaining information on the exact time.
If you only want to receive information about the exact time from the Internet, and synchronize manually, use the services of one of the so-called Daytime servers. Before connecting to such a server, make sure you have a console Telnet client (it is found in both Linux and many versions of Windows). Run the telnet program with the parameter consisting of the server's IP address and port number, separated by a colon. The port number for the Daytime protocol is always 13. For example: telnet 22.214.171.124:13
In response, you will receive information about the time and date, after which the connection will be automatically disconnected. Ignore the clock - the server is in a different time zone. You only need information about minutes and seconds. Use only those servers from the list that are explicitly stated to support the Daytime protocol. Never connect to the same server more than once every four seconds inclusive, otherwise your IP address will be blocked (your requests will be mistaken for a DoS attack).
To synchronize the computer clock with the server automatically, you will have to use another protocol - NTP. It is supported by all servers from the specified list, even those that do not use the Daytime protocol. However, it is best to use a more accurate NTP server for this - ntp.mobatime.com. The public pool of time.windows.com servers is somewhat less accurate. Please note that the URLs of these servers are written without the usual string "https:// www". In no case should requests to any NTP servers be repeated more often than once every four seconds, inclusive.
To automatically synchronize the built-in computer clock with the NTP server in Linux operating system, first install the ntp package. Then enter the command: sudo ntpdate (NTP Server URL)
To have the time automatically synchronized with the NTP server in the Windows operating system every time the computer is turned on, select the "Date and Time" item in the "Control Panel". Switch to the "Internet Time" tab. Check the box "Enable synchronization with a time server on the Internet." Enter the URL of the NTP server in the only field on the page.
Install the Server Time J2ME application on your mobile phone. After launching it, enter the URL of the NTP server in the settings. Then select the "Start!" Item from the menu. After the request is made, you can compare the time on the server with the time in the built-in clock of the phone. The synchronization will have to be done manually, despite the use of the NTP protocol. This is because the Java virtual machine on the phone does not allow applications to change the system clock.