# Suppressing the retrieval date in biblatex-apa

I was wondering why biblatex-apa was not suppressing the urldate from being printed. So I looked around and I found the question Odd date output from biblatex-apa, but found out that it was more about the format of the date.

The American Psychological Association style manual states that

"Do not include retrieval dates unless the source material may change over time (e.g., Wikis)" (American Psychological Association, 2010, p. 192)

Question: How do I suppress the retrieval date from being printed (unless perhaps I am citing a wiki)?

bibliography.bib:

@article{myers,
author = {Scott W. Myers and Michael Ballweg and John L. Wedberg},
title = {Assessing the impact of {European} corn borer on corn grown for silage},
url = {http://www.uwex.edu/ces/crops/uwforage/ECB.htm},
urldate = {2013-07-09},
journaltitle = {Focus on Forage},
volume = {3},
issue = {4},
organization = {University of Wisconsin Wisconsin Team Forage},
keywords = {jared},
}


sample.tex:

\documentclass[preview,border=5]{standalone}

\usepackage[american]{babel}
\usepackage{csquotes}
\usepackage[style=apa, backend=biber]{biblatex}
\DeclareLanguageMapping{american}{american-apa}

\begin{document}

\nocite{*}
\printbibliography

\section*{Desired output:}

\begin{minipage}{\linewidth}
\hangindent=24pt
Myers, S. W., Ballweg, M., \& Wedberg, J. L. (n.d.).
Assessing the impact of European corn borer on corn grown for silage.
\emph{Focus on Forage, 3}.
\end{minipage}

\end{document}


I know that I can manually delete urldate from my entry in the bib file but I would rather not do that as I use the same file when working with other citation styles.

Add this to your preamble to remove urldate fields from entries with url fields which don't look like wikis. Of course you can tweak the regexp to your requirements:

\DeclareSourcemap{
\maps[datatype=bibtex]{
\map{
\step[fieldsource=url,
notmatch=\regexp{wiki},
final=1]
\step[fieldset=urldate, null]
}
}
}


This removes urldate from the data stream which biblatex sees dynamically and so you don't need to touch your .bib.

• Thanks for answering this Philip. This did the job. Perhaps this can be fixed in the next version of biblatex-apa? – hpesoj626 Jul 19 '13 at 1:34
• Well it's not part of the style by default because it's not obvious what "(e.g. Wikis)" should mean for everyone. Often users just omit the urldate for URL sources they deem "static". – PLK Jul 19 '13 at 13:07
• I will add this example and a comment to the documentation of the next release of the style. – PLK Jul 19 '13 at 21:41
• Thanks, PLK. I am sure other users will benefit from the example as well. Cheers. – hpesoj626 Jul 19 '13 at 22:02