[time-nuts] June 30 2015 leap second

[Henry Hallam]

The difference between GPS time and UTC (due to leap seconds) is
broadcast in the GPS navigation message[1] so all but the most poorly
designed GPS modules should take care of it and output the correct UTC
time.

I'm not going to get into the mess of unix epoch time.  Basically,
it's not a continuous time scale.  There is some information on the
wikipedia page[2], and plenty of discussion on various mailing lists
such as LEAPSECS.

Henry

[1] Specifically, page 18 of subframe 4 - see IS-GPS-200G page 112,
114 and 119-121.
[2] https://en.wikipedia.org/wiki/Unix_time#Leap_seconds

On Tue, Jan 6, 2015 at 1:01 PM, d0ct0r <time at patoka.org> wrote:
>
> Hello,
>
> As I am in the process of creation of my own Nixie clocks. And it probably
> good time frame to clarify one thing about leap seconds. In my project I am
> using GPS module as an option to have current UTC time and also to have 1PPS
> signal to do auto-adjustment for external RTC module. The question is how
> usually GPS modules handle leap seconds ? Is it satelates who send UTC time
> to GPS module or GPS module has firmware with leap second information
> hard-coded ?
> The same question is for UNIX epoch time. How computers knows if it is
> necessary to add leap seconds ? Lets say I am using very simple script to
> calculate UNIX time for specified date:
>
>
> ========================================================
> #!/usr/bin/perl
>
> use Time::Local;
> my ($d, $m, $y);
> my $time;
>
>
> @myYears = ('01/06/2000', '01/06/2015', '01/06/2038', '01/06/3000');
>
> foreach (@myYears) {
>         ($d, $m, $y) = split '/', $_;
>         $time = timelocal(0,0,0,$d,$m-1,$y);
>         printf "%ld\n\r", $time;
> }
>
> ======================================================
>
> It will produce the following output:
>
> 959832000
> 1433131200
> 2158977600
> 32516740800
>
>
> I am not sure if its take leap second consideration. Most likely not. And
> that means its only accurate for the present and pas time. Right ? For my
> clock I already implement the function for the leap second and I am able to
> add/remove number of seconds from the time I receiving from GPS or any other
> source. But it will be more inetersting if clock could do it "automagically"
> and shows me that famous "60" number without human interaction. Any advise
> for this ? Thanks !
>
> Regards,
>
> V.P.
>
>
> On , Tom Van Baak wrote:
>>
>> Just announced: there will be a positive leap second at the end of
>> June 30 2015 UTC (that's Wednesday July 1st for most of the world).
>>
>> As usual we time nuts will have a leap second party -- where we
>> capture and share the magic hh:59:60 display on as many different
>> clocks and instruments as possible.
>>
>> /tvb
>>
>> More info:
>> ftp://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat
>> http://hpiers.obspm.fr/eop-pc/
>>
>> And for those of you who want to know how long each day really is:
>> ftp://hpiers.obspm.fr/iers/bul/bulb_new/bulletinb.dat
>> _______________________________________________
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>
>
> --
> WBW,
>
> V.P.
>
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