Getting hyperref to work with \citeyear and \citeyearpar in biblatex

One has to redefine the citation commands instructing to use hyperlink, namely:

\DeclareCiteCommand{\citeyear}
    {}
    {\bibhyperref{\printdate}}
    {\multicitedelim}
    {}

\DeclareCiteCommand{\citeyearpar}
    {}
    {\mkbibparens{\bibhyperref{\printdate}}}
    {\multicitedelim}
    {}

Another alternative is to use the \cite* command which is provided by all by all author-year and author-title styles. See the manual, section 3.7.2 "Style-specific Commands".