Time Signal and Standard Frequency Stations :
For many radio listeners, this was the only 'legal' attempt
for listening to utility stations. When all other stations were
illegal to listen to, time signal and standard frequency stations
always were legal, and publications noted them as a normal part
of the radio spectrum. So, many utility dxers started their career
with hunting for these signals...:
Today, the importance of these transmissions to the scientific
community has decreased, on the other hand, there is now more
public use. For example, in many countries you may operate 'radio-controlled'
clocks, which often derive their time from the longwave stations
listed here. Also, some shortwave radios have a distinct 'WWV'
preset function to present you their actual time announcement.
Now, with this latest update (December 2011), there are a few stations included, that are no real 'time signal stations' at all. The one is a station from the US - Defence Civil Preparedness Agency, which was transmitting time announcements, but who's real purpose was to be able to survive an atomic war, and to give instructions for those few still alive. The other station is from Uruguay - they did not have their own 'voice mirror', they used their local telephone time announcement for identification and adjustment on international radiotelephone circuits. That's why they were know as 'La Senal...'
There is an official list of time signal stations, which is quite informative. But please be aware, that some official institutions pass changes of their stations a little bit slowly to international organizations. And please keep in mind, that this is an annually renewed list - but this link may help you to find next year's list!