UTC (Coordinated Universal Time) is the global civil timescale used by millions of people, businesses and authorities across the globe. UTC is based on the time told by caesium atomic clocks. These clocks are the most reliably accurate chronometers on Earth, able to maintain accurate time for several millions of years whilst neither losing nor gaining a second.
Unfortunately caesium clocks are far too expensive and delicate pieces of machinery to make it practical for us all to have one but fortunately the time that they tell is transmitted by several countries. These nation’s national physics laboratories tend to broadcast the UTC time from these clocks by long-wave.
In the UK the 60 kHz transmission is broadcast by the National Physical Laboratory from a transmitter in Anthorn in Cumbria (it was based in Rugby until 2007). NPL constantly maintain the transmissions and assess its accuracy. Whilst the MSF signal is a British based transmission is possible to receive the signal in some parts of northern Europe and Scandinavia.
However, in mainland Europe, the strongest time and frequency signal is the German transmission broadcast from Frankfurt in Germany. This signal known as the DCF is controlled and maintained by the German National Physics Laboratory. While Switzerland also has its own time and frequency signal, the German DCF signal is by far the most widely used in Europe.
In the USA a similar system is maintained by NIST (National Institute for Standards and Time) and is broadcast from Fort Collins, Colorado. This signal is known as WWVB and is available in most parts of Northern America (including Canada).
Japan maintains its own timing broadcast (JJY) also which is popular in the south pacific and several other countries (such as France) maintain their own signals too although these tend to have only minor coverage.
All these times signals operate in a similar fashion. The strength of the signal is either reduced by between 6 and 10 dB or switched off for a specific amount of time before being restored at the start of each second. The amount of time the signal is reduced indicates a stream of binary numbers with positioning markers.
The signals operate on a 60 kHz frequency and carry a time and date code which relays the following information in binary format: Year, month, day of month, day of week, hour, minute, DUT1 (the difference between UTC and UT1 which is based on the Earths rotation). The signals also relay information about local time such as British Summer Time.