How do you tell the time?

A simple enough question, I would think. Most people would reply with: “I look at my watch.” Or, if they are younger, maybe: “I look at my cell phone.” In any case, there are numerous sources of time all around us. However, there is the question of accuracy. How do you set your watch etc. to the precise time?

Many years ago, there was no standard time and all anyone could use was the position of the Sun. When church clocks became commonplace, the hourly chime was the source of all temporal knowledge. In recent years, we have turned to technology, but that brings its challenges …

When I was a kid, the common way to check the exact time was to telephone the “speaking clock”. This was a low cost call, which would be answered by a recording of a lady with a rather plummy accent, who would say something like “At the third stroke, it will be three fifteen precisely” and this would be followed by three “pips” [short bleeps]. It seems that you can still access it in the UK by dialing 123 or you can hear a modern version of it here. I am sure that a similar service was available in most countries.

For the last three decades, my reference point for timekeeping would be the radio. The BBC broadcasts “the pips” at the top of the hour and these are well known to be accurate. But lately, this has become unreliable because of advancing technology. Digital radio seems to have what appears to be a fixed lag, so the pips are always late. If, indeed, the lag is predictable, then I do not understand why the BBC have not simply compensated for it when they broadcast the time signal. Nowadays, I listen to the radio mainly through the Internet and here there is a non-deterministic lag. I have noticed that, if I play the same radio station in two rooms with my Sonos system [and do not tell it to synchronize them], there can be several seconds difference between the two.

I am not really that challenged, however. I have a number of clocks that receive a radio signal [from somewhere] that keeps them adjusted correctly [and even handles the madness of daylight savings] and my phone adjusts for timezones too. It seems that young people eschewing watches have the right idea.

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This article first appeared on the Siemens Digital Industries Software blog at https://blogs.sw.siemens.com/embedded-software/2012/04/19/how-do-you-tell-the-time/