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Leap Second


npts2020

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The intent of the leap second concept is to make it so that only the people who truly care about precise timing are the ones have to worry about it. Even then, most of those who care about precise timing don't have to worry about adding a leap second because they get timing information from radio (WWVB) or from the internet (NTP).

 

Common clocks are off by quite a bit more than one second, so the insertion of a leap second doesn't really matter to us ordinary mortals who simply use clocks to time our meals, tell us when to get up to go to work, or tell us when to go to the conference room for the all-important 10:00 AM all-hands meeting.

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Don't forget to add a second onto your timepieces at midnight GMT. Apparently we have to do this so that high noon won't be at 1 pm in a few hundred years.

 

GMT won't have a leap second added, since it's already there. GMT is basically the same as UT1, which is terrestrial time.

 

UTC, on the other hand, is based on atomic time and will have a leap second.

 

We do this mostly for the astronomers, so that they know where objects are in the sky based on the time. A couple of arcseconds can be pretty big in the context of telescopes.

 

 

Pedantic, yes, but that's my job.

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GMT won't have a leap second added, since it's already there. GMT is basically the same as UT1, which is terrestrial time.

My eyes glazed right over that "midnight GMT". To be even more pedantic than swansont, GMT is an obsolete concept. Time as measured by an atomic clock has been the standard for some time now: TAI (International Atomic Time; the acronym is apparently backwards because the acronym is properly in French). Swansont mentioned also mentioned UT1 and UTC. UTC is what is broadcast on the US radio station WWVB (and others) and via internet as Network Time Protocol (NTP). UTC is simply TAI plus or minus an integral number of seconds, the cumulative number of leap seconds. UT1 is an after-the-fact determined version of time tied to the Earth's rotation. Those aforementioned leap seconds keep UT1-UTC between -0.9 seconds and +0.9 seconds.

 

Pedantic? Yes. Important? Depends on who you talk to. Mind-numbing? Ask the guy (PhD in astronomy) on our team I assigned to be our expert on time. He still hates me for that assignment (not really). His exact words: "A pedantic pile of <expletive> replete with pre-scientific nomenclature plus angels-dancing-on-a-pin arguments about which time frame is best suited for dynamics."

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Apparently the addition has caused problems for owners of Microsoft's "Zune" music player, causing the unit to lock up until after noon in 1/1. Shades of the 2000 changeover. :)

 

The lockup happened well before, though. I read speculation that it was a leap year problem, which is unrelated to leap seconds. (Revolution discrepancy causing a calendar correction vs rotation discrepancy causing a clock correction)

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Yeah, it happened earlier- on the 366th day of 2008. Apparently, there was a bug in the Zune clock driver (not written by microsoft). Someone forgot about leap years. :doh:

http://www.zuneboards.com/forums/zune-news/38143-cause-zune-30-leapyear-problem-isolated.html

I think it's been fixed already though.

---

I just re-read it. I guess they had considered leap years, the code was just implemented incorrectly. And nothing has been "fixed"- disconnecting and reconnecting the batter resets the date so it works again (at least for 4 more years).

Edited by NeonBlack
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On something like this I wonder why they don't just ignore it and let the device simply accept a new time value from the central server when it gets its next routine software update.

 

Most systems will do something similar to that — they'll get their NTP signal and update the clock when they do their next synchronization.

 

Any system that requires a time stamp at the level of a second, though (e.g. financial institutions), would need to add it, as would all of the NTP servers disseminating the signal.

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Damn! Now they tell me about the leap second!

 

I was 1 second too early today! :-( Could have slept for 1 second longer. Could have arrived at work 1 second later today. Should have had more coffee today (ok, that's unrelated).

 

I could have logged in to read this thread 6 days ago... Another good reason to be online on the forum 24/7!

 

And regarding GMT, TAI, UT1, UTC... I live by DCT, Dutch Coffee Time... which is about now.

 

*runs off to take a leap coffee*

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Alternatively, you could do what I do: I set my alarm clock roughly 19 minutes ahead in a vain (and fruitless) attempt to overcome my procrastinating ways. Since my clock is already 19 minutes off, that extra one second error from ignoring leap seconds is irrelevant.

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Alternatively, you could do what I do: I set my alarm clock roughly 19 minutes ahead in a vain (and fruitless) attempt to overcome my procrastinating ways. Since my clock is already 19 minutes off, that extra one second error from ignoring leap seconds is irrelevant.

 

But you know it's 19 minutes fast and you do the math (making what we call a paper clock) so you know what time it really is, and you're still late.

 

So you subscribe to my service (still in the planning stage) wherein I set your clock ahead and unknown and random amount each day (from 0-20 minutes fast), so you can't assume that it's really off.

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Impressive, how we all thought that we got 1 second "for free", and now we wasted several minutes talking about it in this thread.

 

The leap second is a fraud, and we were all tricked by it!

 

Leap seconds are the interest accrued from daylight savings. It compounds, and we'll get more as the years go by.

 

:)

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I like to think that it's some kind of airmiles system where you just get a leap second because you've earned it through consuming enough seconds in your life. I'm now saving for my leap decade.

Sorry for not taking this thread very serious. It's a bit of a leap thread if you ask me.

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