Date and Time Notation

On this page
[Summary of ISO 8601] [Campaign for Use of ISO 8601]

Although there is a metric unit of time (the second), there is no such thing as metric time. There have been several proposals, over the years, to decimalize the way we express time at least for the hours, minutes and seconds in a day. None of them ever caught on.

The International Organization for Standardization (ISO) has, however, published a standard for date and time notation. That standard is ISO 8601. It provides a consistent and logical method for expressing year, month, day, hour, minute and second. It avoids the confusion with respect to the difference between US practice (month, day, year) and non-US practice (day, month, year) and, by using a 24-hour clock, avoids ambiguities and the issue of the use of a.m. or p.m. for noon and midnight.

The ISO 8601 standard applies only to dates and/or times that are written in all-numeric form. For dates, ISO 8601 provides no guidance for the non-ambiguous case where the month is spelled out ("long date" format). 

In the United States, implementation of ISO 8601 in new documents and systems is rare, even though the capability to use it already exists in PC operating systems, such as Windows, where the ISO 8601 format is an implicitly selectable option via the Date and Time tabs of the Regional Settings Control Panel applet. For instructions for Windows or for the Macintosh, click on one of the following:


Union Jack (United Kingdom Flag) A Summary of the International Standard Date and Time Notation
Click here to view ISO 8601 Summary and Clarification

Markus Kuhn, of Cambridge University, has a very informative page, summarizing and clarifying the ISO 8601 standard.

[Top of this page]
Union Jack (United Kingdom Flag) Campaign to Get the Internet World to Use the International Date Format
Click here to view ISO 8601 Campaign Site

Here, Steve Adams makes a very emphatic case for the adoption of the ISO 8601 standard. He emphasizes, though, that he is not campaigning to change the way we express dates in an informal context (e.g., in speech).


For a copy of the actual ISO 8601 document, go to Downloadable SI Documents.

[Top of this page]

On this page
[Summary of ISO 8601] [Campaign for Use of ISO 8601]


 

1999-2007, WFP Consulting