Article 21. Determination of date.

21.1. Date to be adopted. Except as provided in Article 3, the date to be adopted as the date of publication of a work and of a contained name or nomenclatural act is to be determined in accordance with the following provisions.

21.2. Date specified. The date of publication specified in a work is to be adopted as correct in the absence of evidence to the contrary.

21.3. Date incompletely specified. If the day of publication is not specified in a work, the earliest day on which the work is demonstrated to be in existence as a published work is to be adopted as the date of publication, but in the absence of such evidence the date to be adopted is

21.3.1. the last day of the month, when month and year, but not day, are specified or demonstrated, or

21.3.2. the last day of the year when only the year is specified or demonstrated.

21.4. Date incorrect. If the date of publication specified in a work is found to be incorrect, the earliest day on which the work is demonstrated to be in existence as a published work is to be adopted. In the absence of evidence as to day, the provisions of Article 21.3 apply.

21.5. Dates of work issued in parts. If parts of a work were published on different days, the date of publication of each part is to be separately determined.

21.6. Range of dates. If the date of publication specified in a work is a range of dates, the work is to be dated from the final day of the range; however, if evidence demonstrates that the date so determined is incorrect or that the work was issued in parts, the date or dates of publication are to be determined according to the relevant provisions of Articles 21.3-21.5.

[amended]

21.7. Date not specified. If the date of publication is not specified in a work, the earliest day on which the work, or a part of it, is demonstrated to be in existence as a published work is to be adopted as the date of publication of the work or of that part. In the absence of evidence as to day, the provisions of Article 21.3 apply.

21.8. Advance distribution of separates and preprints. Before 2000, an author who distributed separates in advance of the specified date of publication of the work in which the material is published thereby advanced the date of publication. The advance issue of separates after 1999 does not do so, whereas preprints, clearly imprinted with their own date of publication, may be published works from the date of their issue (see Glossary: "separate", "preprint").

[amendment]

21.7. Date not specified. If the date of publication is not specified in a work the earliest day on which the work, or a part of it, is demonstrated to be in existence as a published work is to be adopted as the date of publication of the work or of that part.

21.7.1. In the absence of evidence as to day, the provisions of Article 21.3 apply.

21.7.2. Works issued as electronic copies are required to state a date of publication (Article 8.5.2), even if incompletely specified (Article 21.3).

21.8. Advance distribution of separates and preprints. Advance distribution of separates or preprints affects date of publication as specified by the following criteria:

21.8.1. Before 2000, an author who distributed separates in advance of the specified date of publication of the work in which the material was published thereby advanced the date of publication.

21.8.2. The advance issue of separates after 1999 does not advance the date of publication, whereas preprints on paper, unambiguously imprinted with their own date of publication, are published works from the date of their issue, if they fulfil the criteria for publication in Article 8 and are not excluded by Article 9 (see Glossary: "separate", "preprint").

21.8.3. Some works are accessible online in preliminary versions before the publication date of the final version. Such advance electronic access does not advance the date of publication of a work, as preliminary versions are not published (Article 9.9).

21.9. Works issued on paper and electronically. A name or nomenclatural act published in a work issued in both print and electronic editions takes its date of publication from the edition that first fulfilled the criteria of publication of Article 8 and is not excluded by Article 9.

Recommendation 21A. Publication on other than specified date. An author, editor or publisher should not publish, permit to be published, or distribute a work, in whole or in part, for the first time other than on the specified date of publication. An author who receives separates in advance of the specified date of publication should not distribute them until he or she is certain that the work has been published.

Recommendation 21B. Simultaneous publication of relevant data. An editor or publisher should require that all matter submitted by an author and affecting the availability of a new scientific name, including type fixation, be published in the same work and on the same day [Recommendation 10A].

Recommendation 21C. Specification of date. An editor or publisher should state the day of publication of a work, and of each component part of a serial publication, and of any work issued in parts. In a volume made up of parts brought out separately, the day of publication of each part, and the exact pages, plates, maps, etc. that constitute it, should be specified.

Recommendation 21D. Retention of information on date. A librarian should not remove, or allow to be removed by a binder, the cover or pages bearing information relevant to the date of publication, the contents of the work or its parts, or the day or dates of receipt by the library.

Recommendation 21E. Bibliographic information on separates and preprints. An author, editor or publisher should ensure that a separate contains a complete bibliographic citation of the original work (including its date of publication) and has the same pagination as that work. Preprints, incorporating their own date of publication, should be identified clearly as such.

Recommendation 21F. Correction of date. If an author of a new scientific name or other nomenclatural act is aware that the date specified in the work containing it is incorrect or incomplete, he or she should publish a correction in some suitable manner.