It has been called the longest-running feature on CBC Radio. 

The National Research Council's official time signal was first broadcast on CBC Radio 75 years ago on Wednesday. 

On Nov. 5, 1939, as the Second World War was breaking out in Europe, Canadians first heard "the beginning of the long dash" which officially indicated the arrival of 1 p.m. eastern standard time.

Since 1939, the time signal has been broadcast regularly on CBC Radio, allowing Canadians to set their clocks to the exact time set by the NRC. 

The signal served an important role in the pre-digital age, allowing Canadians access to exact time in a world of analog clocks which were not always reliable. 

In today's age of instant communications, GPS systems and 24-hour business transactions, the official time set by the NRC is perhaps even more important. People can now access accurate NRC time whenever they want on their computers and cellphones.

The long dash

John Bernard, discipline leader, Measurement Science and Standards, at the NRC, said the story of the time signal being broadcast on CBC actually has its roots as far back as 1924.

At that time, the Canadian National Railway had a radio station called CKCH, which began broadcasting the time signal from the Dominion Observatory in Ottawa at 9 p.m. every day. Eventually that station was bought by the Canadian Radio Broadcasting Commission, the precursor to the CBC. The CBC began broadcasting the signal in 1939, where it has run ever since.

For Canadians wondering what the meaning of the "long dash" system is, it has nothing to do with Morse code, as some may think. John Bernard said that system originated in the 1920s, when radio was in its infancy.

"Back in the old days, when they didn't have voice announcements, they would have certain seconds missing so that somebody who just picked up the radio broadcast would be able to identify the time of day by the code of missing seconds," said Bernard.

The NRC has a continuous live stream with CBC in Ottawa, and the official time is then broadcast out to each region for the official time signal. CBC employees then introduce the "long dash", at which point the NRC broadcast begins.

The science of time

To determine the official time, the NRC uses atomic clocks, which are instruments that use microwave signals and atoms to provide the most accurate time known in the world. The NRC has a minimum of three atomic clocks running at any given time to ensure that there will always be backups in case one breaks or is inaccurate.

John Bernard said he isn't aware of any time when the NRC clocks have not been accurate.

"They keep extremely good time," said Bernard.

"They probably gain only a few microseconds in a year."

Along with the CBC broadcast, the NRC also runs a shortwave radio station from Ottawa that sends out the time signal. The NRC also sends out a time signal through the Network Time Protocol, which is what's used to set time on most personal computers.