How to get the lettering in \citeyear?

Question

I have the following document

\documentclass[12pt,a4paper]{report}
\usepackage{fontspec}
\usepackage{xunicode}
\usepackage{polyglossia}
\usepackage[maxlevel=3]{csquotes}
\usepackage{graphicx}
\usepackage[style=authoryear, language=french]{biblatex}
\setmainfont[Ligatures=TeX]{FreeSerif}
\setmainlanguage{french}
\setotherlanguage{english}
\usepackage{placeins}

\usepackage{setspace}
\onehalfspacing

When, for instance, I use the code:

\parencite{Boin2000} and \parencite{Boin2000b} 

I get the following result:

Boin, 2000a and Boin, 2000b

But when I use the code:

\citeyear{Boin2000} and \citeyear{boin2000b}

I only get:

2000 and 2000

Boin2000 and Boin2000b are related to the following .bib document:

@Book{Boin2000,
Title                    = {The Politics of Environment},
Author                   = {Boin, Mathis},
Publisher                = {Cambridge University Press},
Year                     = {2000},}

and

 @Book{Boin2000b,
 Title                    = {What is Environment},
 Author                   = {Boin, Mathis},
 Publisher                = {Environment Policies Review},
 Year                     = {2000},}

What should I do to also get the letters "a" and "b" that differentiate the two different references with \citeyear?

Answer 1

That \citeyear does not print the additional letter (the extrayear field) makes sense if you think about the application of the \citeyear command: It is used to write things like "In 2000 Foo finally succeeded in publishing the proof.", not to identify a citation; that is where other cite commands such as \cite, \textcite come in.

\citeyear has a starred variant \citeyear* that also prints the extrayear. From the code this might lead to complications if the labeldate was not actually taken from date but from origdate (for example), then extrayear pertains to origdate, not to date, but the letter is affixed to origdate.

These first two solutions do not have hyper-linking enabled by default though.

You can suppress the mentioning of the author in authoryear and authortitle styles with \cite*. When using a authoryear style this effectively amounts to only printing the year (the labelyear actually) and extryear if need be.

If for some reason \cite* does not work (or has not been implemented in custom styles) and you are concerned about the corner case for \citeyear* I mentioned above, we can define it ourselves by

\DeclareCiteCommand{\citelabelyear}
  {\boolfalse{citetracker}%
   \boolfalse{pagetracker}%
   \usebibmacro{prenote}}
  {\printtext[bibhyperlink]{\iffieldundef{labelyear}
   {\printfield{year}}
   {\printfield{labelyear}%
    \iffieldundef{extrayear}
      {}
      {\printfield{extrayear}}}}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

MWE

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[style=authoryear,backend=biber]{biblatex}
\usepackage{hyperref}
\addbibresource{biblatex-examples.bib}

\DeclareCiteCommand{\citelabelyear}
  {\boolfalse{citetracker}%
   \boolfalse{pagetracker}%
   \usebibmacro{prenote}}
  {\printtext[bibhyperlink]{\iffieldundef{labelyear}
   {\printfield{year}}
   {\printfield{labelyear}%
    \iffieldundef{extrayear}
      {}
      {\printfield{extrayear}}}}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\begin{document}
  \citeyear{knuth:ct:b} and \citeyear{knuth:ct:c}

  \citeyear*{knuth:ct:b} and \citeyear*{knuth:ct:c}

  \cite*{knuth:ct:b} and \cite*{knuth:ct:c}

  \citelabelyear{knuth:ct:b} and \citelabelyear{knuth:ct:c}
\end{document}

Answer 2

This isn't really an answer, but I figured it'd be too long for a comment...

I really need a MWE like this to know if this is a duplicate question or not. Are you using biblatex and if so, what version? There is a chance that your question has already been answered here, which describes a bug that an update might fix.

If you're not using biblatex or that question does not apply to your situation, we at least need to see what your .bib contents for boin2000 and boin2000b look like. These are user defined labels, so I don't think they tell us very much, in and of themselves.

Edit:

I've been able to reproduce your problem with biblatex v2.9a using the following MWE

\documentclass{article}

\usepackage{filecontents}
\begin{filecontents*}{test.bib}
@Book{Boin2000,
Title                    = {The Politics of Environment},
Author                   = {Boin, Mathis},
Publisher                = {Cambridge University Press},
Year                     = {2000},}
@Book{Boin2000b,
Title                    = {What is Environment},
Author                   = {Boin, Mathis},
Publisher                = {Environment Policies Review},
Year                     = {2000},}
@Book{Anderson2003,
author      = {Anderson, John D.},
title       = {Modern Compressible Flow},
publisher   = {McGraw-Hill},
year        = {2003},
}
\end{filecontents*}

\usepackage[backend=bibtex,style=authoryear]{biblatex}
\addbibresource{test}

\begin{document}
    My first citation should be \citeyear{Boin2000}, my second \citeyear{Boin2000b}, and my third \citeyear{Anderson2003}.
    \printbibliography
\end{document}

which results in

and reproduces your problem. Asking around to see if this is still a bug in version 2.9a...