The date on which the cited work was examined
Some online resources are changing so quickly that a citation (<citation> or <nlm-citation>) to the resource is not complete without the date on which the cited resource was examined, since a day before or a day later, the relevant material might be different.
For extensive examples of formatted <nlm-citation>s including use of <access-date>s in <nlm-citation>s, see: Sample PubMed Central Citations. To see tagged versions of these examples, see: Sample PubMed Central Citations - XML Tagged.
<!ELEMENT access-date (#PCDATA %access-date-elements;)* >
Text, numbers, or special characters, zero or more
... <ref> <nlm-citation citation-type="book"> <person-group person-group-type="author"> <name> <surname>Lawrence</surname> <given-names>Ruth A</given-names> </name> </person-group> <source>A review of the medical benefits and contraindications to breastfeeding in the United States [Internet]</source> <year>1997</year> <month>10</month> <access-date>cited 2000 Apr 24</access-date> <publisher-loc>Arlington (VA)</publisher-loc> <publisher-name>National Center for Education in Maternal and Child Health</publisher-name> <page-count count="40"/> <comment>Available from: <ext-link ext-link-type="url" xlink:href="www.ncemch.org/pubs/PDFs/ breastfeedingTIB.pdf">http://www.ncemch.org/pubs/PDFs/ breastfeedingTIB.pdf</ext-link> </comment> </nlm-citation> </ref> ...