[10] [DFN[EDTF]]
は、
曖昧性を含む[[日時]]や[[期間]]の[[記述形式][日時形式]]です。

[11] 
[TIME[2012年][year:2012]]に[[米国議会図書館]]によって制定されました [SRC[>>1]]。

[12] 
その後 [[ISO]] に提出されて[[非互換変更]]が加えられ、
[TIME[2019年2月][2019-02]]に
[[ISO 8601-2:2019]] 
の一部として出版されました [SRC[>>9]]。

* 仕様書

[REFS[
-[5] [CITE@en-us[Extended Date Time Format (EDTF) Specification (Library of Congress)]]
([TIME[2019-02-05 02:55:55 +09:00]])
<https://www.loc.gov/standards/datetime/edtf.html>
- [9] [[ISO 8601-2]]
]REFS]


[18] 
>>5 昔はもっとちゃんとした仕様書があったのに [[ISO]] 
版 (有料) が出版されて削除されてる。
普及させたいのかさせたくないのかわからん。


* 関連

[SEE[ [[BDF][Bibliographic Datetime Format]] ]]

* 歴史

[8] オリジナル版 [SRC[>>1]]
と ISO 版 [SRC[>>9, >>5]]
で[[非互換変更]]があって問題となりました [SRC[>>6, >>7]]。

[1] [CITE@en-US[Extended Date/Time Format (EDTF) 1.0 Submission]]
( ([TIME[2012-09-12 00:28:54 +09:00]] 版))
<http://www.loc.gov/standards/datetime/pre-submission.html>

[2] [CITE@en-us[Extended Date Time Format (Library of Congress)]]
( ([TIME[2012-10-31 22:06:22 +09:00]] 版))
<http://www.loc.gov/standards/datetime/>

[FIG(quote)[
[FIGCAPTION[
[3] [CITE[Top-level Elements and Attributes (MODS Ver. 3 User Guidelines: Metadata Object Description Schema, Library of Congress)]]
([TIME[2016-07-22 06:48:40 +09:00]])
<https://www.loc.gov/standards/mods/userguide/generalapp.html>
]FIGCAPTION]

> edtf – This value is used for dates coded according to Extended Date/Time Format  which in consistent with ISO 8601 but extends it to express special forms of dates that are not covered by w3cdtf and iso8601, such as open ended ranges.
> <dateOther encoding="edtf">unknown/2009</dateOther>

]FIG]


[4] [CITE@en-us[Extended Date Time Format (Library of Congress)]]
([TIME[2015-09-16 22:24:55 +09:00]])
<http://www.loc.gov/standards/datetime/>



[FIG(quote)[
[FIGCAPTION[
[6] [CITE@en[biblatex/CHANGES.md at dev · plk/biblatex]]
([TIME[2019-05-08 18:06:17 +09:00]])
<https://github.com/plk/biblatex/blob/dev/doc/latex/biblatex/CHANGES.md#release-notes-for-version-310>
]FIGCAPTION]

> The recent ISO8601:201x standard supersedes the draft EDTF (Extended Date Time Format) extensions. Biblatex therefore now supports the ISO8601-2 Clause 4, Level 1 Extended Format which is equivalent to the draft EDTF standard but with different syntax. This syntax is in some cases not backwards compatible. Biblatex will not support backwards compatibility for the draft EDTF syntax because it is too messy to do so and few people were using this anyway since it is a relatively new and specialised feature.

]FIG]


[7] [CITE@en[Datetimes. The draft ISO 8601-201x and EDTF. · Issue #656 · plk/biblatex]]
([TIME[2019-05-08 18:14:31 +09:00]])
<https://github.com/plk/biblatex/issues/656>




[13] [CITE@en[GitHub - inukshuk/edtf.js: Extended Date Time Format (ISO 8601-2 / EDTF) Parser for JavaScript]], [TIME[2021-03-01T04:39:29.000Z]] <https://github.com/inukshuk/edtf.js>



[14] [CITE@en[Year zero not treated as a leap year · Issue #21 · inukshuk/edtf.js · GitHub]], [TIME[2022-06-28T02:55:32.000Z]] <https://github.com/inukshuk/edtf.js/issues/21>


[15] 
>>14
これ [[ISO 8601暦]]への理解も [[JavaScript]] [CODE[Date]]
への理解も不十分なまま[[ライブラリー]]作っちゃったってことなのかなあ
(まあ作り始めた当時の [[EDTF]] が [[ISO 8601暦]]だったのかどうかは知らんが)、
不安感あるなあ

[16] 未修正のまま何年も放置されてるのがやばい

[17] [CITE@en[season range not recognized · Issue #12 · inukshuk/edtf.js · GitHub]], [TIME[2022-06-28T03:04:45.000Z]] <https://github.com/inukshuk/edtf.js/issues/12>