I’ve produced the calendar below with TikZ but I think the colourings need to be made more salient by shading a box around the coloured dates (as there will be four of these years on a page and the colouring gets drowned out). How can I do that?
\documentclass[12pt]{article}
\usepackage{mathptmx}
\usepackage{tikz}
\usetikzlibrary{calendar}
\begin{document}
\begin{figure}
\sffamily\scriptsize
\begin{center}
\makebox[0pt]{\tikz
\colorlet{darkgreen}{green!60!black}
\calendar [dates=2012-01-01 to 2012-12-31,
month list,month label left,month yshift=1.25em]
if (Sunday) [black!50]
% GROUP 1
if (between=2012-08-09 and 2012-08-12)[orange]
if (between=2012-06-01 and 2012-06-03)[orange]
if (between=2012-04-05 and 2012-04-07)[orange]
if (between=2012-12-22 and 2012-12-27)[orange]
% GROUP 2
if (between=2012-09-10 and 2012-09-15)[blue]
if (between=2012-08-17 and 2012-08-21)[blue]
if (between=2012-06-29 and 2012-07-02)[blue]
if (between=2012-05-14 and 2012-05-21)[blue]
% GROUP 3
if (between=2012-11-02 and 2012-11-09)[darkgreen]
if (between=2012-01-01 and 2012-01-27)[darkgreen]
;}
\end{center}
\end{figure}\end{document}
\contour
.