Re: What day is 2010-01-02 (and what time is it)

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On Mar 18, 2010, at 12:47 PM, Patrik Fältström wrote:

On 18 mar 2010, at 17.38, Marshall Eubanks wrote:

This is backwards. Most astronomers I know regard UTC as a nuisance. In their calculations, astronomers use TAI (or, if they need to know the rotation of the Earth, UT1). Solar system ephemeris work uses ephemeris time, for historical reasons (ET − TAI = 32.184 seconds). GPS internally uses GPS time, which has the leap second adjustment appropriate for the start of the series in 1980, supposedly because the GPS program office didn't understand leap seconds (TAI - GPS = 19 seconds).

Hmm...the signal for the GPS include the difference nowadays, right?

This is the internal time standard. GPS receivers report UTC.

Marshall


But, the largest problem I think are daylight savings, and the fact the daylight savings rules change.

We should from IETF point of view review the ical spec, and try to push timezone information away from the objects, and to a central repository. The timezone offset should be calculated based on the geographical location of the event.

I.e. if I (or my application) know something happened at 13:32 on 2010-01-02 in Stockholm, that is I claim the best way of stating when something happened. Even better example is 13:32 at 2123-01-02 in Stockholm, as the chance Stockholm still exists in 2123 is higher than Stockholm use the same daylight savings rule then compared with today.

Of course one should be able to say explicit time related to UTC (or TAI ;-) ) as well, but...I am tired of all applications that do the wrong thing. Specifically in user interfaces.

  Patrik


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