Time Sites and Services in the World

This collection of time sites and services on Internet is made by a first part concerning information about how to receive and to synchronize sources of reference time. A second part reports the organizations active in time measurement. Finally, there is information about the world of traditional clocks as well as Internet clocks. The collection is updated at 1998 March. Anyone can send updates and corrections to the address pollastri@iriti.cnr.it.

right times
Right times through Internet directly synchronized to atomic clocks. The information about the current time and date is sent as www page (html), as amimated clock (applet)  or other formats. The list is ordered by the time zone of each site.

The reading error of these services is generally greater than 1 second, for this reason they are only suitable for manual, low precision synchronizations.

synchronizations through Internet
Server, devices and software for automatic synchronization of computer clocks through the Internet network.

Several time synchronization systems through Internet were developed. The most important is the Network Time Protocol (NTP) that allows the maximum level of reliability, accuracy and automatism. It can be used with almost every type of computer small or big. The maximum accuracy is about 1 millisecond.

synchronizations by navigation systems
Data, software and receivers for time synchronization by electronic navigation systems.

The electronic satellite navigation systems are particularly suitable for high accuracy time synchronization in almost every place on the Earth. among these, the Global Positioning System (GPS) is the most important. The maximum precision is about 1 microsecond.

telephone synchronizations
Synchronization services that can be received on a computer with a modem by a normal telephone call.

The maximum precision is in the order of tens of milliseconds.

broadcasted synchronizations
Time synchronization services that can be received from broadcasted radio or television signals.

The maximum precision is about 1 millisecond.

national authorities
Organizations charged by law of the official time keeping and diffusion in the respective states they belong.

State laws about legal time.

international authorities
Organizations that join national authorities.

other organizations
Organizations that work in time metrology without task of official time keeping.

information about Earth rotation

The changes of the Earth rotation are continuously monitored also with the scope of keeping the correct relation between the Universal Time (UT) and the Universal Coordinated Time (UTC) .

Tutorial Information.

F. Pollastri - The Time of Internet - 19980326