The “Time from NPL” signal in Britain is broadcast on 60 kilohertz and can be received all over Britain and in large parts of northern and western Europe. Both the station’s carrier frequency and the time code transmitted are set by banks of cæsium clocks maintained by the National Physical Laboratory.
Similar time signals are transmitted by the DCF77 station near Frankfurt, Germany and WWVB in Fort Collins, Colorado in the United States. All of these stations use longwave transmissions which avoid the imprecision that bounce and multipath propagation can introduce at shortwave frequencies.
Here is a list of time signal broadcasts from around the world.