When I'm compiling my tex-files, I'm getting this error:

pdflatex> Package biblatex Warning: BibTeX reported the following issues
pdflatex> (biblatex)                with 'xyz':
pdflatex> (biblatex)                - Invalid format of field 'month'.

It is clear what the message want's to say to me :-) But how do I have to format the field? The same question with urldate... is there a website where I can look for formatting guidelines?

The bibtex-entry which causes trouble is for example this one:

    Author = {Ian Foster},
    Date-Added = {2011-03-31 11:56:42 +0200},
    Date-Modified = {2011-05-23 21:42:29 +0200},
    Journal = {GRIDtoday},
    Month = {jun},
    Title = {{What is the Grid? A Three Point Checklist}},
    Url = {http://www-fp.mcs.anl.gov/\~{}foster/Articles/WhatIsTheGrid.pdf},
    Volume = {1},
    Year = 2002,
    Bdsk-Url-1 = {http://www-fp.mcs.anl.gov/%5C~%7B%7Dfoster/Articles/WhatIsTheGrid.pdf}}

EDIT: ok I found the mistake: the month field must have the format month=6. I have to tell BibDesk to write it that way without {} around it :-)

  • 1
    No, the month just needs to be numeric. month={6} is a completely valid format for the field.
    – Alan Munn
    May 23 '11 at 20:52
  • 3
    I'm getting the error with Month={6}, with Month=6 not :-/ That's the reason for my other question with bibdesk...
    – strauberry
    May 24 '11 at 5:55
  • Then make a MWE with two sample bib entries that shows exactly the error you are getting and add it to that question.
    – Alan Munn
    May 24 '11 at 10:54
  • I think this is the answer you were looking for: tex.stackexchange.com/a/28240/160474
    – geras
    May 9 '19 at 12:11

From the biblatex documentation:

2.3.8 Date Specifications

The date fields date, origdate, eventdate, and urldate require a date specification in yyyy-mm-dd format. Date ranges are given as yyyy-mm-dd/yyyy-mm-dd. Partial dates are valid provided that date components are omitted at the end only. You may specify an open ended date range by giving the range separator and omitting the end date (e. g., yyyy/). See table 2 for some examples of valid date specifications and the formatted date autmatically generated by biblatex. The formatted date is language specific and will be adapted automatically. If there is no date field in an entry, biblatex will also consider the fields year and month for backwards compatibility with traditional BibTeX. Style author should note that date fields like date or origdate are only available in the bib file. All dates are parsed and dissected into their components as the bib file is processed. The date components are made available to styles by way of the special fields discussed in § See this section and table 7 on page 126 for further information.

  • I accepted your answer because of your hint to the right place in the documentation. Thank you!
    – strauberry
    May 23 '11 at 19:54

Using the biber backend for biblatex like so


also lets you use the three-letter abbreviations in your bib file.

If you are on Ubuntu > 12.10 you can install biber by clicking the button below

(source: hostmar.co)


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