[ale] OT ntp - leap second - how many knew what this was 3 weeks ago

[Ron Frazier (ALE)]

Hi Justin,

I found this interesting from the Wikipedia article:

quote on ->

For example, to compute the elapsed time in seconds between two given UTC past dates requires consulting a table of leap seconds, which needs to be updated whenever a new leap second is announced. Moreover, it is not possible even in theory to compute accurate time intervals for UTC dates that are more than about six months in the future.

<- quote off

A classic math problem some teachers might present to math or programming students is "find your age in seconds" etc. I now know that that's impossible in the past without a leap second table and totally impossible in the future.

Sincerely,

Ron


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Please excuse my potential brevity.

(To whom it may concern. My email address has changed. Replying to former
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address. Please send all personal correspondence to the new address.)

(PS - If you email me and don't get a quick response, you might want to
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Ron Frazier
770-205-9422 (O) Leave a message.
linuxdude AT techstarship.com


Justin Goldberg <justgold79 at gmail.com> wrote:

I knew that a year in "rotational time" lasts 365 days, 6 hours, and
0.xx seconds. The 6 hours accounts for the leap day but I suppose the
leap second is only once every few years. I'll defer to wikipedia for
facts.

http://en.wikipedia.org/wiki/Leap_second



On 7/4/12, Ron Frazier (ALE) <atllinuxenthinfo at techstarship.com> wrote:
> Hi all,
>
> Around the beginning of this year, I was doing quite a bit of research into
> ntp and gps and eventually set up my own gps based ntp time server in both
> Linux and Windows. At the end of June, a leap second was inserted into the
> time sequences of the clocks on Earth. For those that may not know what that
> is, the atomic clocks are coordinated with the earth's rotation, so, for
> example, when the clock says noon, the sun is always roughly overhead.
> However, the earth's rotation speeds up and slows down at times.
> So,sometimes, we have to tweak the clocks to match the earth again. At the
> end of June, an extra second was inserted. Normally, the seconds go 58 ...
> 59 ... 00. This time, they went 58 ... 59 ... 60 ... 00. As it turns out,
> this crashed a number of servers.
>
> I find this very interesting, and somewhat scary as a potential programmer.
> Since I'm thinking of learning programming again, and since I have an
> interest in timekeeping, I have considered writing a world clock program
> etc., to show the time in different parts of the world. However, prior to my
> NTP research, I never knew about the leap second. So, there would have been
> a good possibility, had I written the program prior to this year, that my
> program would have crashed as well.
>
> So, my question is, how many of you knew about leap seconds prior to this
> incidence of it and prior to my describing it. If you were writing a clock
> program, would you have known to account for this?
>
> Sincerely,
>
> Ron
>
>
> --
>
> Sent from my Android Acer A500 tablet with bluetooth keyboard and K-9 Mail.
> Please excuse my potential brevity.
>
> (To whom it may concern. My email address has changed. Replying to former
> messages prior to 03/31/12 with my personal address will go to the wrong
> address. Please send all personal correspondence to the new address.)
>
> (PS - If you email me and don't get a quick response, you might want to
> call on the phone. I get about 300 emails per day from alternate energy
> mailing lists and such. I don't always see new email messages very
> quickly.)
>
> Ron Frazier
> 770-205-9422 (O) Leave a message.
> linuxdude AT techstarship.com
>


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