[10] EDTF は、 曖昧性を含む日時期間記述形式です。

[11] 米国議会図書館によって制定されました >>1

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





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

[1] Extended Date/Time Format (EDTF) 1.0 Submission ( ( 版)) http://www.loc.gov/standards/datetime/pre-submission.html

[2] Extended Date Time Format (Library of Congress) ( ( 版)) http://www.loc.gov/standards/datetime/

[3] Top-level Elements and Attributes (MODS Ver. 3 User Guidelines: Metadata Object Description Schema, Library of Congress) () https://www.loc.gov/standards/mods/userguide/generalapp.html

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>

[4] Extended Date Time Format (Library of Congress) () http://www.loc.gov/standards/datetime/

[6] biblatex/CHANGES.md at dev · plk/biblatex () https://github.com/plk/biblatex/blob/dev/doc/latex/biblatex/CHANGES.md#release-notes-for-version-310

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.

[7] Datetimes. The draft ISO 8601-201x and EDTF. · Issue #656 · plk/biblatex () https://github.com/plk/biblatex/issues/656