Richard Mallett wrote:
> Astronomers use yy/mm/dd hh:mm:ss ...
Well, yes and no :-)
This matter is governed by an ISO standard.
More strictly, it has been governed by a
whole sequence of ISO standards. Look it
up in Wikipedia...
The current standard (if you don't wait
too long before opening this message) is
ISO 8601 which permits several possibilities
but none begin yy and none have strokes.
You may write:
2009-08-07 06:05:04
but this is ambiguous since it doesn't specify
the time zone or the time system (UTC, TT, GPS
and so on) and a trailing Z is used for UTC:
2009-08-07 06:05:04Z
This representation is regarded as having two
separate fields, one for time and one for date
but it may be compressed to:
20090807 060504Z
You cannot omit the space separator but you are
permitted to use a T instead:
20090807T060504Z
The T heralds Time and this representation is
regarded as having a single field.
The Standard seems to be silent on fractions of
seconds, so I am not sure whether 321 milliseconds
after the time in my examples really may be shown
as:
20090807T060504.321Z
You may specify a time zone offset in hours and
minutes ahead of or behind UTC and this is shown
*instead* of the Z.
I now propose to annexe an island at just over
50 degrees East and, as Head of State, I shall
decree that the Time Zone is 3h 21m ahead of
UTC. This will make sundial design easier and
will permit a time such as:
20090807T060504+0321
Maybe you didn't want to know any of this?
Frank King
Cambridge, U.K.
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