[tz] historic sub-second time offsets

[Arthur David Olson]

> The tz database has always eschewed sub-second offsets.

This was a result of the early work being focused on supporting
non-sub-second functions such as "localtime;"
absence of sub-second timestamps in early versions of UNIX also played a
role.

We might expect TZDBv6 to have sub-second offsets, as well as Julian
calendar support, Persian calendar support, and noon typing (solar, local
mean, civil:-)

    @dashdashado

On Wed, Nov 5, 2014 at 10:47 AM, Steve Allen <sla at ucolick.org> wrote:

> From their inception the International Time Bureau (BIH) produced
> records of the deviations between various time sources.  I have a
> sampling of those BIH publications from 1960 in images here
>
> https://plus.google.com/photos/112320138481375234766/albums/6078225731350227361
>
> 1960 is after the availability of cesium atomic chronometers and
> during the era when Heure Definitive was UT2.  These pages include
> part of the initial attempt to "coordinate" radio broadcasts between
> the US NBS station WWV and the UK NPL station MSF.  They include time
> offset plots for various observatories for the entire year of 1960,
> and a couple of pages of the radio broadcast offsets for the end of
> the year.  Also note that these data were not published until as much
> as a year after the measurements, and only then could one know what
> time it should have been.
>
> From the turn of the 20th century it was agreed that everyone would
> use the same the technical basis for determining civil time, but the
> quality of time available in any particular place depended on
> available resources and training, so the implementation was imperfect.
> In many countries the observatory time was the legal time, and the
> broadcast time signals were, practically, the official time.
> Plowing through these historic records of time offsets only makes
> sense for projects such as re-reducing occultation data.
>
> The tz database has always eschewed sub-second offsets.
> The data on these pages show part of why that is a good thing.
>
> --
> Steve Allen                 <sla at ucolick.org>                WGS-84 (GPS)
> UCO/Lick Observatory--ISB   Natural Sciences II, Room 165    Lat  +36.99855
> 1156 High Street            Voice: +1 831 459 3046           Lng
> -122.06015
> Santa Cruz, CA 95064        http://www.ucolick.org/~sla/     Hgt +250 m
>
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