[LEAPSECS] sunrise time is the solution!

Rob Seaman 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

> daylight

> saving time also provides an answer to the leap second question.


> http://catless.ncl.ac.uk/Risks/25.10.html#subj1


> 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

> latest

> 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

> hours

> 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

> no

> 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),

> just

> 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

> situation.


> * Small timezone adjustments are less disruptive than large ones.


> * Frequent timezone adjustments make timezone-related bugs more

> obvious

> and therefore easier to fix.


> * It preserves the role of Earth location scientists in time keeping.


> Tony.

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