Reference time sources
DCF77 – The abbreviation stands for: D: Germany, C: long wave transmitter, F: Frankfurt am Main, 77: transmission frequency 77.5 kHz.
The time signal transmitter DCF77 is a long wave transmitter in Mainflingen near Frankfurt am Main. DCF77 is the callsign assigned to the transmitter. With a range of 1,500 km, it provides Germany and western Europe with the legally valid time. The transmitter has an accuracy with a relative standard deviation of the transmitted time of 10-12 maximum, which corresponds to an error of one second in 30,000 years.
GPS – The Global Positioning System (GPS) is a global navigation satellite system for determining positions on Earth. The satellites each have an atomic clock and send out the exact time via GPS signal. In order to receive the signal, an antenna with a clear view of the sky is required. GPS time servers can be used anywhere in the world.