Sorry, LG I got side tracked when I started writing etc, hence the mess of my previous post !.
As an example, Police investigating a serious / major crime. CCTV cameras are identified in 20 different locations and 4 detectives are sent out to 5 locations each to download and seize the recordings.
Due to human error and laziness, most cctv terminals do not have the correct time programmed into the system which is usually displayed on the screen of subsequent recordings. To ensure a consistent and accurate way to determine any discrepancies each detective will ring the BT speaking clock and compare it to the cctv terminal they are currently working on then evidence this information in an official witness statement. Furthermore, the cctv footage from the 20 different locations can later be synchronized for accuracy using one trusted method as opposed to each individual detective using their own individual methods (sun-dials etc).
This should phase out soon as more and more officers are being issued with portable computer devices that are all connected to the same operating system.
There are numerous other situations but hopefully this one example helps. I am sure you can appreciate the need for accurate timing as evidence and putting the pieces together in serious crime investigations.