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. --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial