Year calculations with datetime2 and pgfkeys

I would like to add years to a given date (without having to care about leapyears).
I should be able to define the date via pgfkeys and after that add years to this date.
For example 01.01.2020 -> +2 -> 01.01.2022 and so on.
The following approach fails in several points in the code (probably due to expansion problems in the DTM-commands)

documentclass{scrartcl}
usepackage{pgf}
usepackage{datetime2}

pgfkeys{mydate/.initial}

newcommand{addyear}[2]{
    DTMsavedate{mydate}{#1}
    pgfmathparse{int(DTMfetchyear{mydate}+#2)}
    pgfmathresult-DTMfetchmonth{mydate}-DTMfetchday{mydate}
}

begin{document}
    %%% define date via pgf keys
    pgfkeys{/mydate={2020-01-01}}

    %%% print date without changing
    Date (raw): pgfkeysvalueof{/mydate}, 
    % Formatted:  DTMdate{pgfkeysvalueof{/mydate}}     %   <- not working

    %%% add one year
    Date (raw): addyear{2020-02-02}{2}
    % Date (raw): addyear{pgfkeysvalueof{/mydate}}{2}             %   <- not working
    % Formatted:  DTMdate{addyear{pgfkeysvalueof{/mydate}}{2}}   %   <- not working
end{document}