September 2, 2019

Date Display - existing standards


Part 1: Date standards within healthcare

  • NHS: Clinical usability Guidelines

Part 2: Date standards outside healthcare

  • ISO 8601
  • US Military
  • International Civil Aviation Organization (ICAO): Machine Readable Travel Documents
  • World Wide Web Consortium (W3C)
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PART 1: Date standards within healthcare

NHS: Clinical Usability Guidelines

Short date format
Use for healthcare-worker facing applications.

Short date format, with the day of week
Tue 09-Sep-2008

Long Date Format

The long date format is always used when information is produced for patient consumption. Such as handouts, appointment reminders, and forms. Acceptable long date format options include:

09 September 2008

9th September 2008

Tue 08 September 2008

The NHS Date Display CUI document appears quite reasonable to me. It matches my pre-existing options and research to date on date display. Also, in those areas, where CUI has a different approach than I had initially concluded, they have provided sufficient reasons to back up their guidelines, and I have since changed my conclusions to be in line with CUI. For instance, they provide compelling reasons for why a hyphen must always be between date elements, or why a leading 0 in the day field for digits under 10 is a good practice.

This is discussed in further details in the original CUI and other EHR blogpost (Date Display - Short Date (EHR convention)).


NHS, User Interface Guidelines (June 2015, Version Date Display PDF is located here.

Part 2: Date standards outside of healthcare

ISO 8601

ISO 8601 was first published in 1988. It aims to set an international standard for the representation of date and time.

Its advantage is it is the official ISO standard in this area. The standard was recently updated in 2019.

It can handle a wide array of different types of complex dates with precision. Including to include the year, month, week, day, hour, minute, second, time zone, ordinal date, dates without years, and durations.

In order to achieve such broad applicability, it relies exclusively on Arabic numbers and some pre-defined characters (e.g. - : T W Z).

An example of the ISO 8601 format is:  2019-08-09T09:51:05+00:00

Another example is:  2019-08-09

The examples above demonstrate its strength and weakness. The standard is exceptional from a technical perspective in communicating certainty of date.

However, the format fails to score points for human clarity and readability.

The ISO 8601 specification is titled "Date and time — Representations for information interchange". The keyword here is "information interchange". This does not read "date and time reliability for humans".

Therefore, I believe, and others (such as NHS's CUI, W3C, ICAO) that ISO is not an ideal format to display dates for human consumption in a clear and unambiguous manner.

For this reason, ISO 8601 should not be adopted as the default UX display of dates in the EHR.

If groups would like to use this as a standard to store dates in the software’s code, it seems reasonable to me, but I’m not sure what best practices are for that at the moment.

Reference 8601

Wikipedia: ISO 8601

W3C: Use international date format (ISO)

W3C - Date formats, Internationalization (updated 2007) Essentially advocates spelling out the month (rather than using numbers), and using four digits for the date.

US Military

US Military date standards are an example of a standard (day-month-year) within a country that's official standard is (month-day-year)

Short-form:      DD MMM YY      

e.g. 12 Oct 99

Month: three-letter abbreviation. The first character is a capital.

Separator: is a space.

Long-form:   dd MMMM YYYY (month spelt out fully)  

e.g. 12 October 1929

Year: is represented with four digits, only when the month is spelt out completely.


Army Regulation 25–50:  Preparing and Managing Correspondence, 17 May 2013

alt.politics forum: Military date format (2011)!topic/alt.politics/8DGGjYIMEDo

International Civil Aviation Organization (ICAO): Machine Readable Travel Documents

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ICAO is an agency of the United Nations made of 193 member countries and set standards for aviation.

One of its Standards includes that for Machine Readable Passports (Doc 9303). The document was first published in 1980 and traces its ancestor to 1968. As of 2019, it is in its seventh version last published in 2015.

It outlines specifications for  displaying the date on the human-readable part of the passport document:

Day: always shown with a two-digit number

Month: may be either printed in full or abbreviated up to four characters. In cases where the Gregorian calendar is not used, the State may print the month in numerical form. In this case, it is displayed DDnMMnYY or DDnMMnYYYY where n is a single blank space or period.

(The document outlines further details on how both the local language, and the month in English, French, and Spanish must be listed if the national language is not one of these three).

Abbreviations of Months in English, French, and Spanish

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Year: is shown as last two or four digits. "States are encouraged to use the four-digit representation of the year for all date formats."

Separator: a space, or in the all number format a period is permitted instead.

Unknown date of birth = represented with "x" in the part of the date that is unknown, e.g. XX XXX 1975

Different guidelines are specified on the machine-readable component of these documents.

The format prescribed for machines is the YYMMDD format. (e.g. 12 July 1942, becomes 430712).

Furthermore, in the digitally encoded section of the document (Part 10), it specifies that the date is coded as CCYYMMDD.

ICAO, Doc 9303
Part 3: Specifications Common to all MRTDs

World Wide Web Consortium (W3C)

"The World Wide Web Consortium (W3C) is an international community that develops open standards to ensure the long-term growth of the Web."

Final suggestion leaning towards the explicit written month and four-digit year format. in W3C Date Format Q&A


W3C: Date Format:

Use international date format (ISO)

W3C: Date and Time Formats

W3C: Time & date: Essential concepts
A good overview of different ways to represent dates and time

From the series Building the EHR

Section: Conventions / Date Display

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