One of the missions of the Royal Observatory of Belgium is to integrate Belgium into international space and time reference systems. In particular, it carries out the participation of Belgium to the international time scale UTC (Universal Coordinated time) and keeps a precise realisation of UTC, namely UTC(ORB). This realisation is freely distributed via Internet (NTP) enabling anybody to be synchronised with the Belgian Legal Time.

The Time Lab maintains two public NTP servers for time synchronization of PC clocks by Internet. These primary stratum 1 time servers are synchronized on 2 different sources: (1) UTC(ORB), our local realization of UTC; (2) UTC(USNO), broadcasted by GPS satellite system.

The precision of the synchronization between our primary time servers and the different time sources is of a few microseconds (10^-6 seconds). A remote synchronization on our public servers, using the NTP protocol, is directly traceable to UTC with an utmost precision of a few milliseconds (10^-3 seconds) when the synchronization is done in optimal conditions.

The Network Time Protocol (NTP) is the most commonly used Internet time protocol, and the one that provides the best performance. Large computers and workstations often include NTP software with their operating systems.