If you want to set the clock of your computer or mobile device exactly, you can use a service of the physikalisch-Technische Bundesanstalt (PTB), which enables time synchronization via the Internet.

Often, you need to specify the exact time in official traffic and business transactions via the Internet. However, most computer clocks run inaccurately. If you need the exact time on your computer, it is necessary to adjust the computer clock regularly.
For the time synchronization of your computer you can use the services of the PTB.

For time synchronization, 3 time servers are available to you, whose clocks are synchronized directly by the atomic clocks of PTB. Central European Time (CET) or Central European Summer Time (CEST) is the legally valid time in the Federal Republic of Germany.

PTB's servers use the so-called "Network Time Protocol" (NTP) to transmit the time information. With this protocol, the clocks of computers, mobile devices or network components can be synchronized.

For this purpose, programs are required which support the NTP. Such programs are available for all common operating systems.
After installing such a program you have to specify one or more of the following addresses:

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

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