Standard format for Date and Time - ISO 8601 - Applicable and Useful

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The International Standard for representing dates and times with numbers merits note both as an applicable standard that should be considered and applied whenever date and time information is presented, particularly as part of a larger set of data, but also because of some underlying utility inherent in the specified format.  First adopted in 1988, the current International Standard is specified by: ISO 8601:2004 - Data elements and interchange formats -- Information interchange -- Representation of dates and times

The purpose of the ISO 8601 Standard, as summarized in Wikipedia, is "to eliminate possible ambiguity in date/time information, particularly in data exchange."  I know from personal experience the potential for confusion in the representation of dates, because when a Russian writes the date of 5/9/2014, this typically represents the date of 9/5/2014, as written by an American.  Under ISO 8601, the date would be written as 2014-09-05, eliminating possible confusion and avoiding arguments over dinner.  So, take note:

Public Service Announcement: Correct date format

(Thanks to for the acuity in capturing the standard's role and application.  Thanks also to TallTed, who gently upbraided the WhiteHouse for both (i) failing to follow the standard in recently published policy documents: The Digital Services Playbook and TechFAR Handbook and (ii) failing to advise others to conform with the standards.)

Beyond avoiding the occassional international ambiguity, and possible international dispute (over dinner or otherwise) the standardized format provides some functional utility as well, because the format allows for a simple text-based sort on a list dates, as a text, to give a chronological ordering.  Even before I knew of the applicable standard, I used the format (yyyy-mm-dd) to represent dates in various situations where I might want to perform a sort on the date field using ordinary text-based sorting protocols.  I'll come back to this.

Basic Standardized Formats:

While the standard delves into some depth on the details of usage (including specification of standards for representing duration, time interals, and repeating intervals), a few basic formats in the standard worthy of note and adoption:

  • Standard date format:  yyyy-mm-dd (as used: 2014-09-05)
  • Standard time format: hh:mm:ss [or hh:mm] (as used: 22:31:25 [or 22:31])
    • The time standard calls for using 24 hour clock.
  • Combined date/time: yyyy-mm-ddThh:mm:ss (as used: 2014-09-05T22:31:25)

The full standard covers ways to write:

  • Date
  • Time of day
  • Coordinated universal time (UTC)
  • Local time with offset to UTC
  • Date and time
  • Time intervals
  • Recurring time intervals

(a brief summary of the standard can be found at:

(a brief description of details for applying the standard can be found at: Wikipedia summary of ISO8601)

Putting the Standard Format to Use - Simple File Management System

Long ago, I adopted a file-naming practice of including , among other things, a "date stamp" and keywords in all file names, resulting in filenames such as these:

  • "letter_2009-09-01_dgb to joesmith_party of the early parts.pdf"
  • "letter_2009-09-01_joesmith to dgb_party of the next parts.pdf"
  • "motion_2011-04-02_goodclient_summary judgment.docx"

(Note that the date used in the filename is the date of actual "publication," for my purposes (i.e. the date the letter was sent, or the date the motion was filed), which may be different for the standard fields associated with the file, such as "last modified" date, particularly for document files created from a scan of a hard-copy.) 

The micro-bits of information in these filenames simplifies the location of specific documents from a given directory, but also allows for a sorted listing of the directory to provide some useful summary information, because a simple sort on the directory will:

  • group documents of specific types (e.g. grouping files beginning with filename of  "letter_..."),
  • list the documents in each group by date (sorted by "..._2009-09-01").
    • Note that the sorting by date is possible because the date is represented in the "standardized" format.

Thus, a sorted list of files in a dicectory containing the correspondence in a given matter provides a quick overview of the history of correspondence in that matter.  When used in combination with a standardized system of creating directories and sub-directories for specific matters, the directory sturcture and filenames provide a reasonably robust, yet simple to maintain, file management system.