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.
- 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.
- 'full basic' 1 and
- 'full extended' 1 formats
- 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.
- 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:
- The internal workings of Computer Programs.
- Computer Printouts (Satellite Tracking, Log Books, Packet Radio,
Contest Scoring, etc).
- Computer Screens.
- Data Storage.
- Data Interchange (on Packet Radio: both within the headers, and within typed
messages; Log Book Files, Contest Log Files, Satellite Pass Data, etc).
- QSL cards.
- Membership Cards, Certificates, Invoices, Receipts, Magazine Issue Dates.
- Any other computer, or paper, based documentation, data, or correspondence.
- The ISO format completely avoids the American / British date format ambiguity.
- Data and programs become internationally portable, with no possibility of
- The usage of the ISO format for the internal workings of computer programs
usually ensures more compact code, and therefore faster operation.
- The logical left to right Year-Month-Day Hour:Minute:Second precedence makes
computer programming easier. Certain date-related algorithms become trivial
when using this style.
- Using the ISO format and 4-digit years should ensure that software
transitions correctly from 1999-12-31 to 2000-01-01 (programs using only a
2-digit year may produce wrong results).
- Having only one date format allowed on computer program screens and
printouts means that the program works the same for everyone everywhere in
the world; only one program version is required for all markets.
- It removes the need for a whole load of 'Date Format' menu options, making
programs smaller, and easier to write. It reduces the scope for making mistakes.
- Using a fixed format for dates and times makes looking down lists of dates
and times easier.
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
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
- Use 4-digit years when storing or printing dates.
- Use the order Year-Month-Day i.e. biggest first (e.g. 1999-12-31).
- Use Leading Zeroes on digits 00 - 09 for the Month and for the Day number.
- Use the '-' separator. Do not use the '/' separator, this has a different
meaning within the standard.
Ordinal Day of Year ('Ordinal Date')
- Use 4-digit years when storing or printing dates.
- Use the order Year-DayNumber.
- DayNumber is a 3-digit Number from 001 to 365 (366 in a leap-year).
- Use the '-' separator between the year and the Day Number (e.g. 1996-250).
Time of Day
- Use the 24-hour format.
- Use the order Hours:Minutes:Seconds i.e. biggest first.
- Use Leading Zeroes on the digits 00 - 09 for each data field.
- Use the ':' separator (e.g. 23:59:59).
- Specify Dates and Times in UTC whenever possible, following the Date
and/or Time by the letter 'Z'.
- For Zones other than UTC the Local Date and/or Local Time is followed by a
Zone Designator, where East of Greenwich is Positive, and West of Greenwich
is Negative. It is a 4-digit number expressing hours and minutes difference
to UTC; where '+0100' means one hour ahead of UTC (e.g. Central Europe),
'-0500' means five hours behind UTC (e.g. East Coast USA), and '+0430'
means four and a half hours ahead of UTC (e.g. India).
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
- that is, as opposed to the truncated and reduced precision formats.
- 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'.
- 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.