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<pub-date> Publication Date

Container element for the parts of a single date associated with an article’s publication (for example, date preprint was released, date article was published in print).

Usage/Remarks

Of all the dates concerning an article, the publication date is the most important, for discovery, credit, Crossref and other authority registration, and other uses. Therefore the publication date should be tagged using its own semantic element <pub-date>, rather than as an <event> or a <date> element.

Best Practice: Use @iso-8601-date

It is recommended to provide an @iso-8601-date attribute on every <date> element, for better machine processing and interoperability

Best Practice: Don’t Repeat <pub-date>

As part of the article metadata (<article-meta>), the <pub-date> element is allowed to repeat. Each repetition can take a different @publication-format attribute to distinguish which form of publication (for example, print publication, electronic publication, ePub) and a @date-type attribute to distinguish between preprint, publication, re-release, etc.
However, current Best Practice is record only a single <pub-date> at any one time. When a new publication format is produced, any previous <pub-date> elements should be described as <event>s inside <pub-history>. This leaves the <pub-date> as the single source of the latest date of publication.
Season and Date Together
While most publication dates will either be a season and a year (for example, Spring 1999) or a year with a possible day and month (for example, January 1, 1999), sometimes the publication date will identify both the season and date. A publication date of “Spring 1999; January 29, 1999” should be tagged: 
<pub-date publication-format="print" date-type="pub"
  iso-8601-date="1999-01-29">
 <season>Spring</season>
 <day>29</day>
 <month>01</month>
 <year>1999</year>
</pub-date>
<string-date>s within <pub-date>
The Archiving Tag Set allows <string-date> both inside <pub-date> and inside <date>. This is the most flexible scheme for preserving any publisher’s structure. It is recommended that <string-date> inside <pub-date> be reserved for cover dates, and the date component elements (<month>, <day>, etc.) be used inside <pub-date>.
Attributes
assigning-authority
calendar
date-type
iso-8601-date
publication-format
pub-type

Multi-lang Attributes

lang-focus
lang-focus-custom
lang-group
lang-source
lang-source-custom
lang-translate
lang-variant
lang-variant-custom

Base Attributes

id
xml:base
xml:lang
Models and Context
May be contained in
<article-meta>, <event>, <event-desc>, <front-stub>
Description
Any combination of:
Content Model
<!ELEMENT  pub-date     %pub-date-model;                             >
Expanded Content Model
(day | era | month | season | year | string-date |
x)*
Tagged Samples
Article metadata print publication 
...
<article-meta>
 <article-id pub-id-type="pmid">...</article-id>
 <title-group>...</title-group>
 <contrib-group>...</contrib-group>
 <aff id="StLukes">...</aff>
 <pub-date publication-format="print" date-type="pub" 
   iso-8601-date="1999-03-27">
  <day>27</day>
  <month>03</month>
  <year>1999</year>
 </pub-date>
 ...
</article-meta>
...
Article metadata multiple dates 
...
<article-meta>
 ...
 <pub-date publication-format="electronic" date-type="pub" 
   iso-8601-date="2015-10-30">
  <day>30</day>
  <month>10</month>
  <year>2015</year>
 </pub-date>

 <pub-date publication-format="print" date-type="pub" 
   iso-8601-date="2016-01-01">
  <day>01</day>
  <month>01</month>
  <year>2016</year>
 </pub-date>
 <volume>27</volume>
 <issue>1</issue>
 <fpage>25</fpage>
 <lpage>39</lpage>
 ...
</article-meta>
...