Honeychildren web-site notes

ISO 8601 date formats


To ease possible confusion on these web-pages, I have chosen to standardise my date format on the International Organisation for Standardisation (ISO) recommendations laid out in ISO 8601:2000. I have referred to the British Standards Institution BS 7151:1989, which was the latest printed version available to me because they’ve now gone high-tech, but only if you pay! There is a later BSI implementation of the ISO standard numbered EN 28601:1992 or later.

I apologise if you find this confusing at first, although I'm sure you'll soon get the hang of it. The logical part of my brain has always responded positively to 'big-endian' dates since I was first introduced to them in fixed format computer data fields over thirty years ago. I have used them in my own private notes for over fifteen years and once I started encountering those horrendously structured American format dates on the Internet I resolved to start using ISO 8601 on documents for wider circulation. Perhaps I’ve always been a bit contrary, but everyone is used to written time starting with hours (preferably 24 of them!) so I don't see why everyone shouldn't get used to dates starting with years – after all, both measurements are dealing with the same physical quality, time.

ISO 8601 represents date and time information in descending size: year-month-day T (=time) hours-minutes-seconds in either compact or, more usually, extended formats:

ccyy[mm[dd[Thhmm[ss]]]]

ccyy[-mm[-dd[Thh:mm[:ss]]]]

where square brackets indicate successive optional data. So, for example, 20020830T1405 or 2002-08-30T14:05 was just after lunch on 30 August 2002 (local time!).

Because of our proximity to the millennium – the new one started in 2001 by the way – I have not used the truncated representation which omits the century. If only a year and month are to be shown don’t confuse it with a period of years (see next paragraph); for example 2003-04 is April this year not this year and next.

The standard also defines methods of showing periods of time, either by specifing start and end date-times separated by a solidus [ / ], or by the method I use, where the period is specified in numbers of years [Y], months [M] or weeks [W], days [D], hours [H] and so on, introduced by a ‘P’, for example:

2002-08-15/P6W2D

is a period of six weeks and two days starting on 15 August 2002.

If you want to find out more about date and time standards, you can consult an excellent list of sources on the dmoz open directory project.


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