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December 02, 2008 [posted]

Create Date — New Field Indicates When Record Added to PubMed®

graphical image of the letter A

A new date field, Create Date, will be implemented with all PubMed records when the 2009 system is available in mid-December 2008. Create Date is the date the record was added to the database. All records added to PubMed prior to implementation will receive a Create Date equal to Entrez Date (EDAT).

This field will be searchable and rangeable with the search tag [crdt]. Examples:

diet therapy heart diseases AND 2007:2009 [crdt]

hysteria AND "last 6 months" [crdt]

After implementation of Create Date, we will begin our new policy of setting Entrez Date (EDAT) equal to Publication Date (DP) when the record enters PubMed more than twelve months after the date of publication. Fortunately, most citations enter PubMed close to the time of publication, so CRDT and EDAT will usually be the same. For more information about EDAT and upcoming changes, please see PubMed Entrez Date Modification for Older Citations.

The MEDLINE format will display Create Date with the CRDT field tag. The following example shows part of the MEDLINE format for an imaginary article published in January 2008. It enters PubMed April 28, 2009 as shown by CRDT. Because this is over a year after the date of publication, EDAT is set equal to DP.

DP        -  2008 Jan

EDAT   -  2008/01/01 09:00

MHDA  -  2009/05/12 09:00

CRDT  -  2009/04/28 09:00

Create Date displays in the XML format in the PubMedPubDate element with the PubStatus attribute, "entrez." Please note, this date should not be confused with the Date Created field - DA in the MEDLINE format and element <DateCreated> in the XML - which is a date field used for internal processing at NLM.

The PubMed What's New strategy that is used to update My NCBI saved searches and RSS feeds will continue to use EDAT to limit to recent citations so some citations may be missed. Searchers who use My NCBI to save searches that include Create Date in order to retrieve new citations regardless of publication date are advised to save them without the automatic e-mail update option. The search can be run manually by clicking on the name in the list of My NCBI saved searches.

By Annette M. Nahin
MEDLARS Management Section

Nahin A. Create Date — New Field Indicates When Record Added to PubMed®. NLM Tech Bull. 2008 Nov-Dec (365):e11.

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