documentclass[border=10pt]{standalone}%{article}
%usepackage[margin=1cm]{geometry}
usepackage{pgfgantt}
usepackage{graphicx}
usepackage{xcolor}
%usetikzlibrary{positioning}

ganttset{group/.append style={orange},
milestone/.append style={red},
progress label node anchor/.append style={text=red}}

begin{document}

%    begin{figure}
%    centering
    begin{tikzpicture}
        begin{ganttchart}[%Specs
            y unit title=0.5cm,
            y unit chart=0.7cm,
            vgrid,
            %hgrid,
            title height=1,
            %     title/.style={fill=none},
            title label font=bfseriesfootnotesize,
            bar/.style={fill=blue},
            bar height=0.7,
            %   progress label text={},
            group right shift=0,
            group top shift=0.7,
            group height=.3,
            canvas/.append style={name=mycanvas},
            group peaks width={0.2},
            inline]{1}{13}
            %labels
            gantttitle{Project spring 6}{13}\  % title 1
            gantttitle[]{February}{2}                 % title 2
            gantttitle[]{March}{4}                 % title 2
            gantttitle[]{April}{5}                 % title 2
            gantttitle[]{May}{2}                 % title 2

            \
            gantttitle{P1}{1}                      % title 3
            gantttitle{P2}{1}
            gantttitle{P3}{1}
            gantttitle{P4}{1}
            gantttitle{P5}{1}
            gantttitle{P6}{1}
            gantttitle{P7}{1}
            gantttitle{P8}{1}
            gantttitle{P9}{1}
            gantttitle{Vacances de Pâques}{1}
            gantttitle{P10}{1}
            gantttitle{P11}{1}
            gantttitle{P12}{1}\

            %Cahier de charge
            ganttgroup[inline=false]{Requierements specification}{1}{2}\
            ganttbar[progress=0,inline=false]{Writing requierements specification}{1}{2}\
            ganttbar[progress=0,inline=false]{Writing planning}{1}{2}\
            ganttmilestone[inline=false]{Rendu documents}{2} \

            % Analyse
            ganttgroup[inline=false]{Analyse}{2}{4}\
            ganttbar[progress=10,inline=false]{Analyse}{2}{4}\
            ganttmilestone[inline=false]{Rendu analyse}{4} \
            %Specification
            ganttgroup[inline=false]{Specification}{4}{5}\
            ganttbar[progress=0,inline=false]{Specification}{4}{5}\
            ganttmilestone[inline=false]{Rendu specification}{5} \

            ganttgroup[inline=false]{Réalisation}{5}{10}\
            ganttbar[progress=0,inline=false]{Specification}{5}{10}\
            ganttmilestone[inline=false]{Rendu réalisation}{10} \

            ganttgroup[inline=false]{Validation}{10}{12}\
            ganttbar[progress=0,inline=false]{Specification}{10}{12}\
            ganttmilestone[inline=false]{Rendu specification}{12} \

            ganttgroup[inline=false]{Documentation}{1}{12}\
            ganttbar[progress=0,inline=false]{Specification}{1}{12}\
            ganttmilestone[inline=false]{Rendu rapport}{12} \
            %ganttbar[progress=50,inline=false, bar progress label node/.append style={below left= 10pt and 7pt}]{Task B}{13}{24} \ \
        end{ganttchart}
        node [left] at ([yshift=-1.3cm]mycanvas.north west) {Weeks};
    end{tikzpicture}
end{document}