On Jan 15, 2006, at 10:40 PM, John Cowan wrote:

I realize the ALHP has severe problems with this, but I don't approve of the ALHP anyhow (save perhaps tactically, as explained).

Nothing to add to this.  I just continue to enjoy the fact that folks with completely opposite points of view about civil timekeeping have the same low opinion about leap hours :-)

Indeed.  But the sensible approach would be for each State government to fail to omit the hour of the normal spring transition in the year 2700, say.  In that way, AEDT would become TI+1000 and a normal-looking autumn transition would cause AEST to become TI+0900.

You get points for calling it "TI" instead of "UTC".

Countries without DST transitions would have to actually repeat an hour, of course, just as Algeria had to do in 1940, 1956, 1977, and 1981 (the country has repeatedly flipflopped between UTC+0000 and UTC+0100).

...and Algeria had the freedom to do so precisely because UTC existed to function as a worldwide civil timescale that continued uninterrupted "in the background" while the local authorities extemporized.  Presumably you would assert that TI (TAI + constant) could serve this same purpose.  That was presumably the notion of the folks in Torino.  I'm delighted they recognized that UTC should not be redefined.  I disagree that interval time can indefinitely serve as a stand-in for solar time.  It is when the first leap hour (or timezone migration event) occurs that interval time fails the test.  And precisely because it is a timescale that is designed to simply tick, tick, tick in even intervals.

By the way, I re-counted all the secular time zone transitions worldwide.  According to the Olson timezone database, there have been 516 of them since the beginning of standard time (when that is, of course, varies with the country or subdivision thereof).

I think we're using the word "secular" in different ways:

secular 3 a : occurring once in an age or a century
b : existing or continuing through ages or centuries
c : of or relating to a long term of indefinite duration

The ~2 ms per century lengthening of the solar (or sidereal) day is a secular trend.  Overlaid on this trend are all sorts of interesting more rapid periodic and aperiodic effects.  Whatever adjective one might attach to the 516 ad hoc time zone transitions - secular isn't it.

Rob Seaman
NOAO


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