[LEAPSECS] Consensus building 2

Clive D.W. Feather clive at davros.org
Wed Feb 16 08:10:58 EST 2011

Stephen Colebourne said:

> Local time

> * definition: local-time - the time-scale local to a region of the Earth

> * definition: offset - the duration that local-time differs from the

> locally recognised legal standard time-scale

Sorry, that's nonsense. By definition, that "offset" is always zero, since
local-time is always equal to the locally recognized legal standard

What you mean is "the difference between local-time and some global
timescale such as UT1, UTC, or TAI".

> * definition: time-zone - a region of the Earth where local-time is coordinated

"coordinated" with what? Local time in the whole EU (minus those bits in
the Americas) is coordinated, but it's not all the same.

Try "a region of the earth where local time is intended to be the same
throughout that region at any time of the year". Note that there are a slew
of issues that this still glosses over. For example, the UK and Portugal
are currently both in UTx+0100 between certain dates and UTx+0000 the rest
of the year, but in the past they had different changeover dates. Does
this make them one time zone or two? [Olsen finesses this; an Olsen timezone
is a region of a single country, and the "always the same" rule only
applies from 1970 onwards.] As another example, if one country bases its
legal time on UT1 and another on UTC, can they be in the same time zone?

> * the offset from local-time to TAI-2008 can be calculated

given what? And why is this not true for UTC-1972-offset? Or UT1-offset?

> Humanity

> - definition: humanity-day - a non-scientific, commonly used term

> understood by 6bn humans

I don't accept that that is a "commonly used term". Rather, it's a term
you've invented for these discussions, defined by:

> * a humanity-day is interpreted in line with the rising and setting of

> the Sun at a single Earth location

(and I don't have a problem with that, so long as you're honest about it).

Clive D.W. Feather | If you lie to the compiler,
Email: clive at davros.org | it will get its revenge.
Web: http://www.davros.org | - Henry Spencer
Mobile: +44 7973 377646

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