If you want to set the clock on your computer or mobile device precisely, you can use a service provided by the Physikalisch-Technische Bundesanstalt (PTB), which enables time synchronization via the Internet.

You often have to specify the exact time in official and business transactions via the Internet. However, most computer clocks are inaccurate. If you need the exact time on your computer, it is necessary to adjust the computer clock regularly.
You can use the services of the PTB to synchronize the time on your computer.

Three time servers are available for time synchronization, whose clocks are synchronized directly by PTB's atomic clocks. Central European Time (CET) or Central European Summer Time (CEST) is the legally valid time in the Federal Republic of Germany.

The PTB servers use the so-called "Network Time Protocol" (NTP) to pass on the time information. This protocol can be used to synchronize the clocks of computers, mobile devices or network components.

This requires programs that support the NTP. Such programs are available for all common operating systems.
After installing such a program, you must specify one or more of the following addresses:

• ptbtime1.ptb.de
• ptbtime2.ptb.de
• ptbtime3.ptb.de.

Depending on the runtimes in the network connections, accuracies of one to ten milliseconds can be achieved.