\usemodule[gantt]
%\usemodule[gantt][alternative=mp]
%\usemodule[gantt][alternative=tikz]
\setuppapersize[A4,landscape][A4,landscape]
\setuplayout[scale=0.8]
\setuppagenumbering[location=]

\starttext
  \startgantt[xunitlength=0.5cm,style=\tfx,titlestyle=\tfx,drawledgerline=true]{10}{48}
    \startganttitle
      \titleelement{2009}{7}
      \numtitle{2010}{1}{2012}{12}
      \titleelement{2013}{5}
    \stopganttitle
    \startganttitle
      \numtitle{6}{1}{12}{1}
      \numtitle{1}{1}{12}{1}
      \numtitle{1}{1}{12}{1}
      \numtitle{1}{1}{12}{1}
      \numtitle{1}{1}{5}{1}
    \stopganttitle
    \ganttbar{task 1}{2}{17}
    \ganttgroup{a group of tasks}{6}{18}
    \ganttbar{task 2}{5}{10}
    \ganttbar[color=blue]{task 3}{15}{3}
    \ganttbar{task 4}{20}{3}
    \ganttcon{15}{4}{20}{6}
    \ganttbar{task 5}{15}{5}
    \ganttbarcon[color=red]{task 6}{20}{5}
    \ganttbarcon{task 7}{30}{5}
  \stopgantt
\stoptext
