What are the date ranges for past MeSH Indexing years?
The table below contains the date range for each MeSH Indexing year as applied to completed MEDLINE citations. Once a year, generally in mid-November, all MeSH headings on citations are synchronized with the new edition of MeSH. The MeSH Indexing year runs until the next global update of citations. To retrieve all of the MEDLINE/PubMed citations for a specific MeSH Indexing year, search PubMed for the MeSH Indexing year date range followed by the Date Completed field tag [dcom].
|MeSH Indexing Year||Date Range in PubMed Format
Start Date:End Date (Inclusive Dates)
12000 and 2001: Cannot absolutely confirm 2000 and 2001 dates because Year-End Processing (YEP) occurred during NLM reinvention from a mainframe to a relational database environment and an interim YEP system was used.
21990: ending day changed from 25th to 26th to cover 1,956 citations processed by NLM.
31987: ending day changed from 22nd to 23rd to cover 11 citations processed by Kennedy Institute of Ethics (KIE) or NLM’s History of Medicine Division (HMD).
41986: ending day changed from 24th to 29th to cover 43 citations processed by KIE or HMD.
What is the MeSH Indexing year?
Once a year, generally in mid-November, all MeSH headings on citations are synchronized with the new edition of MeSH. The MeSH Indexing year runs until the next global update of citations. The MEDLINE citations within a MeSH Indexing year will have a DateCompleted[dcom] value within the date range for that year.
Until 2000, the MeSH Indexing year ran from approximately late October to late October due to:
- the time lags over the years for the development of the MeSH (Medical Subject Headings) vocabulary,
- the global updating of the vocabulary on the citations, and
- the issuance of printed indexes in the calendar month corresponding to the month on the issue cover (that is, the January issue of print Index Medicus had content indexed up through the end of October).
Since the reinvention of NLM MEDLINE processing from a mainframe computer to a relational database environment in 2000 and the discontinuance of the printed Index Medicus, the MeSH Indexing year runs from mid-November to mid-November. See also Annual MEDLINE®/PubMed® Year-End Processing (YEP): Background Information.
How can I retrieve all of the NLM Journal Citations (MEDLINE/PubMed) for a specific MeSH Indexing Year?
To retrieve all of the MEDLINE/PubMed citations for a specific MeSH Indexing year, search for the date range for the MeSH Indexing year followed by the field tag [dcom].
For example, for the MeSH Indexing year 2003, enter the following search:
This search will return all citations that passed NLM’s quality assurance procedures as of those dates, whether or not MeSH headings were assigned. To retrieve only citations with MeSH Headings that are not from the OLDMEDLINE original set, add this limit:
2002/10/31:2003/11/12 [dcom] AND medline [sb] NOT jsubsetom
(Note that when you run your search, the PubMed Search Details will show the [dcom] search tag as [CDAT].)
Progression of MEDLINE Updating Frequency
- Monthly updating was in place through calendar month March 1988.
- Semi-monthly updating began with calendar month April 1988 (June 1988 Entry Month data). Semi-monthly updating applied to calendar months January through October. Calendar months November and December reverted to monthly update.
- Weekly updating began with calendar month June 1990 (August 1990 Entry Month data). Weekly updating applied to calendar months January through October. Calendar months November and December reverted to monthly update.
- Daily updating (5 times per week, Tuesday - Saturday) began January 9, 2002 and continues through the present.
Starting in August 1996, the PREMEDLINE database made in-process MEDLINE citations available in advance of the completely MeSH-indexed citation. Date of Entry, the day that the citation was available in electronic format for users, did not carry over to the completely MeSH-indexed version of the citation. A new Date of Entry was assigned under the mainframe computer workflow in use at that time. As of 2/2/2001 PREMEDLINE no longer exists as a “separate” entity; it became part of the reinvented MEDLINE workflow in the relational database environment.
DateCreated versus DateCompleted
During NLM reinvention in late 2000, a distinction was defined between Date of Entry and Date of MeSH indexing. Date of Entry was renamed DateCreated. Date of MeSH indexing was introduced as a new element called DateCompleted. During conversion from the mainframe environment, all journal citations had DateCompleted populated using the value from the old Date of Entry. Citations newly created in the relational database environment received both a DateCreated and a separate (and usually different) DateCompleted. DateCompleted also applies to citations that are not MEDLINE status; some citations undergo NLM Quality Assurance procedures but do not get MeSH Headings assigned. These citations include Retraction of Publication [Publication Type], out-of-scope citations (also referred to as PubMed-not-MEDLINE citations, typically in the general science/chemistry journals), older back issue citations submitted by publishers prior to the journal’s acceptance for MeSH indexing, and “PubMed-only” citations generated from the article being deposited in PubMed Central.
The chart above does not apply for OLDMEDLINE citations that originated from machine-conversion of the old, print indexes (jsubsetom). For these citations, the DateCreated (DA) element corresponds to when the original keywords were assigned. DA is not directly searchable in PubMed.
DA is displayed in PubMed as follows:
In the MEDLINE format: DA - 19511201
In the XML format:
The 4-digit year is sufficient to identify the year of the printed index in which the citation originally appeared.
DateCompleted for OLDMEDLINE citations corresponds to when the citation appeared online for the first time.
On a very small number of citations, the jsubsetom citation subset value may have been merged onto an existing MEDLINE citation. This condition can happen when a citation was published in a pre-1966 print index, but was also duplicated in a post-1965 print index. NLM will keep the post-1965 print index citation and add data from the pre-1966 print index to it. In this case, DateCompleted is the date for when the MeSH was added to the citation.
Most OLDMEDLINE citations have current MeSH; of these, the citations that have all their keywords mapped to current MeSH have had their status changed from OLDMEDLINE to MEDLINE. They retain jsubsetom as a citation subset value, though. See //www.nlm.nih.gov/databases/databases_oldmedline.html for an explanation of the mapping of the original keywords to current MeSH.
Last Reviewed: November 10, 2021