[tz] What's "right"?

Steve Allen sla at ucolick.org
Thu Nov 12 22:34:58 UTC 2020

On Thu 2020-11-12T14:05:18-0800 Guy Harris hath writ:
> In that context, what is a "time scale"?  Does it assign an hour/minute/second value to each second?

A time scale assigns labels to points in time.

TAI is the best effort for those points in time to be equidistant in a
general relativistic reference frame that resembles the surface of the

For TAI those labels may be simply a continuous count of seconds, but
it is traditional to give names based on civil calendars and clocks
even though those TAI labels differ systematically from calendar days
measured by watching the sky from the earth.

> so UTC is also a "time scale".

Which shares the same second markers at TAI, but applies different
labels that over the long run do not systematically differ from
calendar days measured by watching the sky.

>       A positive or negative leap-second should be the last second of a UTC month ...
> suggesting that the clock is tied to a calendar in some fashion.

The Gregorian calendar is used for UTC.

Steve Allen                    <sla at ucolick.org>              WGS-84 (GPS)
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