[LEAPSECS] sunrise time is the solution!
seaman at noao.edu
Fri Dec 26 12:32:59 EST 2008
One might have pointed out that the quoted Risks article was from the
April 1st issue :-)
On Dec 23, 2008, at 7:10 AM, Tony Finch wrote:
> It occurs to me that my proposal for a rational replacement for
> saving time also provides an answer to the leap second question.
> The essence of sunrise time is that we reset our clocks each day to a
> fixed time when the sun rises at a benchmark location. For the UK, the
> benchmark location would be where the Greenwich meridian crosses the
> Tropic of Cancer. The fixed time is 06:44, which is the time of the
> sunrise at that location according to mean solar time (UT1). The
> reset is
> accomplished by adjusting your timezone offset, which you'd do a few
> earlier than sunrise to avoid disrupting early risers, and you'd
> round the
> offset to the nearest minute to avoid breaking things like ISO 8601.
> If you are setting civil time according to these rules, then civil
> time is
> by definition coupled to the rotation of the Earth, and there can be
> accelerating secular difference between the two. This is true whatever
> time scale you use as the basis from which timezone offsets are
> calculated. You have a pretty free choice of basis timescale long as
> its length of day is not too far from the Earth's LOD.
> The resulting system has several useful properties:
> * You can use atomic time as your basis timescale, with a LOD of 86400
> SI seconds.
> * The only other time(s) you need to worry about are local time(s),
> like the current situation.
> * Both basis time and local time have fixed-length minutes and hours,
> which is much simpler than the current situation.
> * Basis time has fixed-length days, which is also a simplification.
> * Local time has variable-length days, just like the current
> * Small timezone adjustments are less disruptive than large ones.
> * Frequent timezone adjustments make timezone-related bugs more
> and therefore easier to fix.
> * It preserves the role of Earth location scientists in time keeping.
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