A Common Date-Time Standard for Amateur Radio - A Proposal

Author: Ian Galpin, G1SMD.    Last revised: 1996-Jul-28.

Copied to: <http://www.qsl.net/g1smd/isoham.htm> on: 1998-Oct-22.


  1. That the provisions of the: within the International Standard ISO 8601 2 , for representation of: be adopted as defacto standards for all facets of the Amateur Radio hobby.
  2. That an unofficial variant to the ISO standard, that allows the month to be written as the common 3-letter English abbreviation be included within this proposal, when a Calendar Date is intended for human reading.
  3. That the UTC time scale be used whenever possible in Date and Time Representations.


The usage of these formats can apply to each of the following:



Dates have caused many problems to computer programmers. The tradition in the past has been to use the dd/mm/yy form in Britain, and the mm/dd/yy form in America. The problem is that programs from abroad may 'work backwards' to how the user expected them to. In addition, messages written abroad from the eventual reader, may be misunderstood: e.g. 1/12/96 is read in Britain as 1st December, but if written by an American it is likely that January 12th was intended. The ISO Year-Month-Day format solves this problem.

Where only a 2-digit year is used within a computer program, there may be problems when year '99' (1999) rolls over to '00' (2000); in addition to the problem that a date like 31/06/96 may be 1896, 1996, or 2096!

The full ISO format (with 4-digit years) removes all of these problems at the same time.

The Standard was originally adopted in Britain as BS 4760:1971, and as BS 5249:1976 and later superseded by BS 7151:1989. Latterly, and as a result of European harmonisation, BS 7151 has been renumbered as BS EN 28601, so implementing the European Standard EN 28601, which is identically worded to the ISO 8601 Standard. International Standard ISO 8601 replaced the ISO 2014, ISO 2015, ISO 2711, ISO 3307 and ISO 4031 Standards which have all been withdrawn; but which you may see referred to in some older documentation.

The ISO 8601 Standard has now been adopted in most countries of the world.

Summary of the ISO Standard

Gregorian Calendar Date

Ordinal Day of Year ('Ordinal Date')

Time of Day

Time Zones

Various Comments

When combining Dates and Times, always put the Date BEFORE the Time.

The formats described above are the 'Full' format. The ISO standard also specifies formats for various 'Truncated' and 'Reduced Precision' forms. For the Full Format Calendar Date of '1996-05-25', the Truncated version of '96-05-25' says year 96 in any century, and the Reduced Precision '1996-05' form, just specifies the Date down to month level. The Full Format is the most relevant here; the other forms may cause problems of misinterpretation in some instances (especially problems when a 2-digit year is used).

For each definition within the Standard, there is a 'Basic Format' and an 'Extended Format' style. The Extended format (1996-05-25) includes the separators, and is intended for human reading. The Basic format does not include the separators (19960525), and is intended for data storage (e.g. on Hard Disk), or for Data-Interchange, and can be an ASCII string, packed BCD, a binary number, or whatever you choose.

The Standard defines that a Date and/or Time expressed in the UT or UTC time scale should be followed by the letter 'Z'. For Amateur Radio operators it may be prudent to also allow the letters 'UT' or 'UTC' be used.

For a Date and/or a Time expressed in a Local Time Zone, the standard defines a sign and 4-digit numerical format for expressing that Time Zone relative to UTC. For Amateur Radio purposes, I propose that the established 3-letter abbreviation for Zone, where already defined and in common usage, also be allowed (e.g. EST, PST, PDT, CET, CST, etc).

The ISO Standard allows Dates and Times to be expressed in only fully numeric form. For human reading of dates and times; and to help those people who may not have come across the ISO Year-Month-Day way of specifying Dates and Times before; and for the purposes of this proposal, it would be wise to also allow, within the definition for Calendar Date and Time, the usage of the common English three letter abbreviation of the Month to be used, such that the date 1996-05-25 can also be written as 1996-May-25.

Notes to this Proposal

  1. that is, as opposed to the truncated and reduced precision formats.

  2. ISO 8601 is adopted throughout Europe as EN 28601.
    EN 28601 is adopted in Britain as BS EN 28601.
    ISO 8601 is adopted in America as an ANSI standard.
    ISO 8601 is the Default National Standard in Denmark, Sweden, most East European countries, China, Korea, Japan, and many others.
    The Title of the ISO Standard is 'Data Elements and Interchange Formats - Information Interchange - Representation of Dates and Times'.

  3. ISO 8601 also has other provisions for Date expressed as Week and Day of Week, and for specifying Periods of Time. These are not especially relevant to Amateur Radio, and are not covered by this proposal.

Author: Ian Galpin, G1SMD
Last revised: 1996-Jul-28

This document is CopyRight Ian Galpin, 19 Palmer Road, Poole, Dorset, England, BH15 3AR. Permission is given for distribution via Internet and via magnetic media only. No fee may be charged for this distribution and the document shall be passed on in full, no alterations are permitted. For permission to reprint or use in a business environment, write to the author at the address above. Comments and suggestions on any Y2K or related topic are also always welcomed.

Year 2000 and ISO 8601.

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