Inconsistent brackets in references generated by biblatex

Question

Using the following commands

\usepackage[style=numeric, backend=biber, seconds=true, date=iso, urldate=iso, maxcitenames=2]{biblatex}
...
\printbibliography[heading=bibintoc]    

seems to result in inconsistent brackets around the publishing date. The first reference has no brackets, the next three do, and the fifth does not again. Can someone explain this to me? The journal does not have citation requirements other than "that they are consistent", so if this is consistent in some sense, it is fine I guess.

Answer 1

The output you see is consistent in way: The publication year of @articles is in parentheses, that of other types is not.

As for why that is the case we can only speculate. The year information is usually implied by volume and number of an @article, so it kind of makes sense to place the year after those in parentheses. (Incidentally the usual German translation of volume in this context is Jahrgang, which already contains the reference to "year".) This is not something that is found only in biblatex's standard styles (though it is a bit less common than other design choices): The Chicago Manual of Style requires a similar behaviour (https://www.chicagomanualofstyle.org/tools_citationguide/citation-guide-1.html).

If you want to get rid of the parentheses, a simple way is biblatex-ext's issuedate field format. You'll just have to switch from style=numeric, to style=numeric-ext,.

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage{csquotes}
\usepackage[backend=biber, style=ext-numeric]{biblatex}
\DeclareFieldFormat{issuedate}{#1}
\renewcommand*{\volnumdatedelim}{\addcomma\space}
\addbibresource{biblatex-examples.bib}
\begin{document}
Lorem \autocite{sigfridsson,worman,geer,nussbaum}
\printbibliography
\end{document}