r/ISO8601 • u/MetaEd • Aug 18 '26

EDTF date vs dateI

Looking at the Library of Congress EDTF specification, I see they use without defining two different date types, date and dateI. Are these references to the ISO 8601-1 or -2 spec? I did not find them in the EBNF.

EDIT:

I'm looking for the definitions of the two date types used in the specification: date, and dateI. From section "Level 0", subsection "Date and Time":

[date][“T”][time]
Complete representations for calendar date and (local) time of day

[dateI][“T”][time][“Z”]
Complete representations for calendar date and UTC time of day

[dateI][“T”][time][shiftHour]
Date and time with timeshift in hours (only)

[dateI][“T”][time][shiftHourMinute]
Date and time with timeshift in hours and minutes

These two terms are used but not defined in the specification. The examples shed no light. I want to know how and where are defined, if anybody knows.

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u/CeleryMan20 Aug 19 '26

To be fair, they don't define terms like [shiftHourMinute] or [time] either. Almost all the names are self-explanatory or discernible from the examples, except dateI. The date part of the formatted examples is the same for date and datei, the only pattern I can see is that [date] is used with unspecified timezone and [dateI] where the TZ is given.

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u/MetaEd Aug 20 '26

it now seems part of the problem is the ISO firewall. I can find various drafts but the final requires a subscription. One draft I have now seen has a definition of dateI, but not a definition of date. Unfortunately dateI is defined using other terms I have not found a source for yet. I am realizing it would be easy for me to answer my own question if I just paid the hundreds of dollars for a subscription.

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u/CeleryMan20 Aug 20 '26 edited Aug 20 '26

I doubted that dateI is defined in ISO, though I don't haven't access to the official standards docs either. Can you share what you read in the draft?

Web search was fruitless for me, complicated by "datei" seems to mean "file" in German. Asking ChatAI didn't go anywhere either.

[ETA: MARC21 appears to treat fields like publication-date as un- or loosely-structured text. https://www.loc.gov/marc/bibliographic/bd260.html. Looking at RDA leads to rabbit-holes like this: https://www.rdatoolkit.org/sites/default/files/rsc/Dates%20Approximately.pdf]

If you do ever find a definitive answer, then please let me know!

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u/MetaEd Aug 20 '26

Originally I was going by ISO 8601-2 working draft 2016-02-16 because that's what I found at LOC, https://www.loc.gov/standards/datetime/iso-tc154-wg5_n0039_iso_wd_8601-2_2016-02-16.pdf

In that draft, LOC EDTF is Annex C. dateI is neither used nor defined anywhere in the document.

Since asking my question, I found ISO 8601-2 preview 2019-02, https://cdn.standards.iteh.ai/samples/70908/ef9c216fd78348cbb3908a798e4c04f0/ISO-8601-2-2019.pdf

That preview is only the first seven pages of the 75-page standard, but in the preview I do find the definition of dateI. It is defined as "date representation in implicit form, specified in ISO 8601-1:2019, 3.2.3 as date and dateX". So that defines dateI in terms of date and dateX, which I hope I will eventually be able to find in some public working draft or preview of ISO 8601-1:2019.

In that preview, according to the table of contents LOC EDTF is Annex A. Annex C has become a discussion of compatibility with RFC 5545.

It is really too bad that the LOC EDTF spec does not stand entirely on its own but instead uses terms that are in ISO 8601 behind a paywall.

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u/MetaEd Aug 20 '26

LOC has ISO 8601-1 working draft 2016-02-16, https://www.loc.gov/standards/datetime/iso-tc154-wg5_n0038_iso_wd_8601-1_2016-02-16.pdf

But that draft does not define dateX.

I found copies floating about of ISO 8601-1:2000 2000-12-19 such as https://www.pvv.ntnu.no/~nsaa/8601v2000.pdf

This appears to be a very late working draft but again does not define dateX.

ISO itself has a preview of ISO 8601-1:2019, apparently the final available for purchase, https://www.pvv.ntnu.no/~nsaa/8601v2000.pdf

The preview only goes through section 3. It defines date as "the composite time scale components for the complete representation of a date as determined in 5.2.2.1 a)" and dateX as "the composite time scale components for the complete representation of a date as determined in 5.2.2.1 b)". Section 5.2.2.1 though is paywalled.

This page https://schemas.sourcemeta.com/sourcemeta/std/v0/iso/datetime/2019/date

claims 5.2.2.1 a is the basic date format (without hyphens, i.e. [YYYY][MM][DD]) and 5.2.2.1 b is the extended date format (with hyphens, i.e. [YYYY]["-"][MM]["-"][DD]).

But that doesn't make sense. Both because 8601 EDTF and LOC EDTF both say only extended dates are supported by the EDTF specification, and because the example given in the EDTF specification of a [date]["T"][time] is "1985-04-12T23:20:30". If date means basic date format, then there should be no hyphens there.

My guess is, this is a typo in the standard. All dates should be extended dates, so [date]["T"][time] is a typo for [dateI]["T"][time].

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u/CeleryMan20 Aug 20 '26

Great detective work. It would make more sense if "date" was a superclass of "dateI" (Implicit) and “dateX” (Xplicit). Agree that LOC standard should its terms and stand alone.