How to Use Extended Date Time Format (EDTF) for Fuzzy Dates

Created by Glen Barnes, Modified on Thu, 3 Apr at 3:04 AM by Natalie Nguyen

Many dates that you may want to record may be ‘fuzzy’ dates, that is they may be uncertain or approximate. For example dates such as “Circa 1953” or “1940s?”. To handle these dates you can enter dates in EDTF format. So what are some rules and examples of use?

What is EDTF?

EDTF (Extended Date/Time Format) is a standardized date format designed to represent precise, uncertain, approximate, and complex dates in a structured way. It is an extension of ISO 8601, developed by the Library of Congress to improve handling of historical, archival, and bibliographic data.

Why does STQRY use EDTF and what are the benefits of EDTF?

Many dates that you may want to record may be ‘fuzzy’ dates, that is they may be uncertain or approximate. For example dates such as “Circa 1953” or “1940s?”.


By using EDTF dates you can record any date, even if you are unsure of the accuracy or if the date is a range of dates.


Rule

Description

 Example

Full Date

Year, month, and day in YYYY-MM-DD format

1941-03-25

Partial Date (Month & Year)

Year and month only in YYYY-MM format

2006-02

Year Only

Just the year in YYYY format

1945

Date Interval

A range between two dates, formatted as YYYY-MM-DD/YYYY-MM-DD

1980/2005-01

Decades

Uses YYYx format to represent a decade

197x

Centuries

Uses YYxx format to represent a century

18xx

Uncertain Date

If the date is uncertain, add a "?"

1984?

Approximate Date

If the date is approximate, add a "~"

1984~

Approximate Decade

A rough estimate of a decade range

1960-1969~

Completely Uncertain Date

If the date is entirely unknown, use "uuuu"

uuuu

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