Re: datetime

From: Martin Hill <mchill-at-dial.pipex.com>
Date: Sat, 23 Apr 2005 01:01:14 +0100


It seems to me that for *most* practical purposes the ISO-8601 form with an assumed UTC is sufficient. As an ignorant layman I thought UTC did indeed have a reference point and a timescale... It may not be ideal, but it seems the ideal needs a bit more thrashing out.

If it's not sufficient, can anyone explain (in ignorant laymans terms please!) why not? Or obviously just point us at something that does so.

What we really want for now is a way of including datetimes in our standard message forms; it doesn't really matter if they're perfectly described yet as the people using them understand the context they're given in.

Cheers

Martin

Arnold Rots wrote:

> Several people have already addressed most of the important points.
> Accurate time needs a specification of time scale and reference
> position. STC contains an astronTimeType that may be helpful.
>
> However, let me say emphatically that JD and MJD (and ISO-8601, for
> that matter), only define something akin to a format and imply nothing
> about the associated timescale. A JD or MJD without a timescale is
> meaningless; UTC cannot be assumed.
>
> - Arnold
>
> Patricio F. Ortiz wrote:
>

>>Julian Date and Modified Julian Date (which do assume the usage of UTC)
>>seem to be one of the most appropriate way of representing such instant
>>in time. Using the ISO standard (string representation) is quite common,
>>but any application wanting to compare instants in time needs to convert
>>it to a floatinng number (double).
>>

>
> --------------------------------------------------------------------------
> Arnold H. Rots Chandra X-ray Science Center
> Smithsonian Astrophysical Observatory tel: +1 617 496 7701
> 60 Garden Street, MS 67 fax: +1 617 495 7356
> Cambridge, MA 02138 arots-at-head.cfa.harvard.edu
> USA http://hea-www.harvard.edu/~arots/
> --------------------------------------------------------------------------
>
-- 
Martin Hill
www.mchill.net
07901 55 24 66
0131 668 8100 (ROE)
Received on 2005-04-23Z00:03:31