[LEAPSECS] BBC radio Crowd Science

[Warner Losh]

On Tue, Jan 31, 2017 at 11:29 AM, Brooks Harris <brooks at edlmax.com> wrote:

> As Steve Summit said earlier (with his 2015 example)
>
> Positive leap second:
>
>     TAI           UTC           TAI-UTC
>     00:00:34.0    23:59:59.0    35
>     00:00:34.5    23:59:59.5    35
>     00:00:35.0    23:59:60.0    35
>     00:00:35.5    23:59:60.5    35

I think these two offsets are wrong. They lead to bad math since 35-35
is 0, but 35-36 is -1 which with borrowing is 60.

>     00:00:36.0    00:00:00.0    36
>     00:00:36.5    00:00:00.5    36

> Attached - TAIToUTCDemoConsole - a rudimentary c program using POSIX
> gmtime() (a pure, strict gmtime() with 1 second resolution) demonstrates one
> way to make the calculations. Its output:
>
> 2016-2017 Leap Second
> TAI seconds  YMDhms (TAI)       TAI-UTC UTC seconds LS  YMDhms (UTC)
> 1861920035 = 2017-01-01 00:00:35 - 36 = 1861919999  0 = 2016-12-31 23:59:59
> 1861920036 = 2017-01-01 00:00:36 - 36 = 1861920000  1 = 2016-12-31 23:59:60
> 1861920037 = 2017-01-01 00:00:37 - 37 = 1861920000  0 = 2017-01-01 00:00:00
> 1861920038 = 2017-01-01 00:00:38 - 37 = 1861920001  0 = 2017-01-01 00:00:01

I think the TAI-UTC offset for the leap second is wrong and should be corrected.

Warner