I will admit to being a little lackadaisical about time, I don't even wear a watch when I'm not flying. But when you are flying, it pays to be accurate. Time is, after all, the foundation of navigation. More about that: Technical / Latitude & Longitude.
Before the days of GPS the frequencies were crawling with time hack stations. Most of those, alas, are gone. The frequencies 5000, 10000, 150000, and 25000 got you something almost everywhere in the world. These days those frequencies are pretty much just in the United States, but you might get lucky.
The National Institute of Standards and Technology (NIST) broadcasts on the following frequencies from the locations noted:
|2.5||40°40'52.2" N||105°02'31.3" W|
|5||40°40'42.1" N||105°02'24.9" W|
|10||40°40'47.8" N||105°02'25.1" W|
|15||40°40'45.0" N||105°02'24.5" W|
|20||40°40'53.1" N||105°02'28.5" W|
Among many sites, there is: http://utctime.org/
Photo: G450 MCDU Nav Ident page, from Eddie's aircraft.