So what time IS it?

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Anyone who routinely loses sleep over even a second of lost video will have listened with interest to all the popular media coverage of the “leap second”. The International System of Units (SI) second is generated from atomic clocks. Man’s natural understanding of time is that the sun is at its highest point in the sky for the day at noon. UTC is the effort to synchronize these two items. The result is that on June 30, 2015 (as has happened 25 times since 1972) a leap second was added to UTC. The last time previous to last week, sites such as Reddit and even Linux were reported to have suffered! So what did your camera and video Management Software (VMS) display?

  • 23:59:58, 23:59:59, 23:59:60, 00:00:00
  • 23:59:58, 23:59:59, 00:00:00, 00:00:00
  • 23:59:58, 23:59:59, 23:59:59, 00:00:00
  • 23:59:58, 23:59:59, 00:00:00, 00:00:01 (and you are now just running a second fast)

So did your system will throw up any alarms or events. Systems do … and should … complain about any gaps or redundancies in time. A one second redundancy or gap, especially on a Leap Second day is pretty easy to explain. A one minute loss of video when a camera “fails over” to non-POE power is a different matter. Some take aways:

  • Understand where your displayed time comes from
  • Understand how your system handles gaps in time
  • Understand how your system handles recurring time
  • Most important is to make sure that performance under these conditions is specified prior to purchasing your system and then tested at the time of commissioning

And the next time someone asks you what time it is ….. Just simply reply UTC, GMT, TAI, PST, PDT, Loran Time, GPS time or StarDate …. If they haven’t run away then they are probably administering a large VMS!

(photo “Prague Townhall Clock” courtesy Flickr user Kainet)

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