Rotate Gantt Chart Figure

Use the landscape-option to turn your page, like this:

 \usepackage{lscape}
 \begin{document}
    \begin{landscape}
    ...your Gantt-Chart here
    \end{landscape}
 \end{document}

To rotate it clockwise, you need to use rotating package:

  \usepackage{rotating}
  \begin{document}
     \begin{rotate}{270}
        ...your Gantt-Chart here
     \end{rotate}
  \end{document}