Cfrgtkky

        documentclass[a4paper,10pt,demo    ]{article} %

    usepackage{pifont} %bouni

    %-----accent

    usepackage[latin1]{inputenc} %écrire directement les accents et il peut poser des problème

    usepackage[T1]{fontenc}

      %-----

    usepackage[colorlinks=true,linkcolor=blue,urlcolor=blue]{hyperref}

     usepackage{graphicx}                    % Enable pdflatex

      usepackage{wrapfig}

      usepackage{amsmath,amsfonts,amsthm}     % Math packages

      %%%%%%%%%%%%% dimension ancien des marges %%%%%%%%%%%%%%%%%%%%

      usepackage{geometry}

      geometry{left=2cm,right=2cm,top=1.5cm,bottom=1.5cm}

      %%%%%%%%%%%%% style des sections %%%%%%%%%%%%%%%%%%%%

     frenchspacing              % Better looking spacings after periods

      usepackage{sectsty}

      sectionfont{%                        % Change font of section 

         command

    usefont{OT1}{phv}{b}{n}%       % bch-b-n: CharterBT-Bold font

     sectionrule{0pt}{0pt}{-5pt}{1pt}}

     %%%%%%%%%%%%%%%% Macros %%%%%%%%%%%%%%%%%%%%

      newcommand{sepspace}{vspace*{1em}}     % Vertical space macro

      newcommand{MyName}[1]{ % Name

        Huge usefont{OT1}{phv}{b}{n} hfill #1

        par normalsize normalfont}

      newcommand{MySlogan}[1]{ % Slogan}{optional)

    large usefont{OT1}{phv}{m}{n}hfill textit{#1}

    par normalsize normalfont}

      %%% ------------------------------------------------------------

      pagestyle{empty}           % No pagenumbers/headers/footers

     %%%%%%%%%%%%%%%%%%%%% Begin Document %%%%%%%%%%%%%%%%%%%%%%%%%

     begin{document}

     %%%%%%%%%%%%%%%%%% Photo et title %%%%%%%%%%%%%%%%%%%%%%%%%

    %---------------------------

   %---------------------------

   MyName{Name Name}

    MySlogan{Curriculum Vitae \ nullhfill  (today)}

    %MySlogan{Curriculum Vitae (October 2016)}

    %---------------------------

    sepspace  % Si on ajoute encore sepspace on aura plus d'espace

    $$$$

     %%%%%%%%%%%%%% Personal details%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    section*{Informations personelles}



    end{document}

I want to add ''th'' in the date as follows

Using datetime package, (see datetime.sty pdf, on p:8):

     documentclass[a4paper,10pt,demo    ]{article} %

      usepackage{datetime}

      newdateformat{dashdate}{%

twodigit{THEDAY}-twodigit{THEMONTH}-THEYEAR}

newdateformat{usvardate}{%

monthname[THEMONTH] ordinal{DAY}, THEYEAR}



    usepackage{pifont} %bouni

    %-----accent

    usepackage[latin1]{inputenc} %écrire directement les accents et il peut poser des problème

    usepackage[T1]{fontenc}

      %-----

    usepackage[colorlinks=true,linkcolor=blue,urlcolor=blue]{hyperref}

     usepackage{graphicx}                    % Enable pdflatex

      usepackage{wrapfig}

      usepackage{amsmath,amsfonts,amsthm}     % Math packages

      %%%%%%%%%%%%% dimension ancien des marges %%%%%%%%%%%%%%%%%%%%

      usepackage{geometry}

      geometry{left=2cm,right=2cm,top=1.5cm,bottom=1.5cm}

      %%%%%%%%%%%%% style des sections %%%%%%%%%%%%%%%%%%%%

     frenchspacing              % Better looking spacings after periods

      usepackage{sectsty}

      sectionfont{%                        % Change font of section 

         command

    usefont{OT1}{phv}{b}{n}%       % bch-b-n: CharterBT-Bold font

     sectionrule{0pt}{0pt}{-5pt}{1pt}}

     %%%%%%%%%%%%%%%% Macros %%%%%%%%%%%%%%%%%%%%

      newcommand{sepspace}{vspace*{1em}}     % Vertical space macro

      newcommand{MyName}[1]{ % Name

        Huge usefont{OT1}{phv}{b}{n} hfill #1

        par normalsize normalfont}

      newcommand{MySlogan}[1]{ % Slogan}{optional)

    large usefont{OT1}{phv}{m}{n}hfill textit{#1}

    par normalsize normalfont}

      %%% ------------------------------------------------------------

      pagestyle{empty}           % No pagenumbers/headers/footers

     %%%%%%%%%%%%%%%%%%%%% Begin Document %%%%%%%%%%%%%%%%%%%%%%%%%

     begin{document}

     %%%%%%%%%%%%%%%%%% Photo et title %%%%%%%%%%%%%%%%%%%%%%%%%

    %---------------------------

   %---------------------------

   MyName{Name Name}

    MySlogan{Curriculum Vitae \ nullhfill  (usvardatetoday)}

    %MySlogan{Curriculum Vitae (October 2016)}

    %---------------------------

    sepspace  % Si on ajoute encore sepspace on aura plus d'espace

    $$$$

     %%%%%%%%%%%%%% Personal details%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    section*{Informations personelles}



    end{document}



  [1]: 

The following uses a datetime2 approach to set the ordinal date, similar to what is proposed in ferahfeza's answer. Additionally, a minor adjustment in the placement of the ordinal is introduced:

documentclass{article}



usepackage[T1]{fontenc}



usepackage{fmtcount}

usepackage[calc,english]{datetime2}

DTMnewdatestyle{usvardate}{%

  renewcommand{DTMdisplaydate}[4]{%

    DTMmonthname{##2} ordinalnum{##3}, number##1 }%

  renewcommand{DTMDisplaydate}{DTMdisplaydate}%

}



makeatletter

AtBeginDocument{

  renewcommand{fmtord}[1]{,fc@textsuperscript{#1}}% Add , before ordinal number

}

makeatother



newcommand{MyName}[1]{ % Name

  Huge usefont{OT1}{phv}{b}{n} hfill #1

  par normalsize normalfont}

newcommand{MySlogan}[1]{ % Slogan}{optional)

  large usefont{OT1}{phv}{m}{n}hfill textit{#1}

  par normalsize normalfont}



begin{document}



MyName{Name Name}

MySlogan{Curriculum Vitae \ nullhfill  (DTMsetdatestyle{usvardate}today)}



end{document}

The culprit is here

1. to find the right layout for your wished date (month day-with-ord, year) and


2. to change the distance between number and ord.

To test this two pints please see the following MWE:

documentclass{article}



usepackage[en-GB,en-CA,en-US]{datetime2}



%usepackage{etoolbox}

%patchcmd{DTMenglishordinal}% <cmd>

%  {#1 DTMenglishfmtordsuffix}% <search>

%  {#1,DTMenglishfmtordsuffix}% <replace>

%  {}{}% <success><failure>





begin{document}



british: 

DTMsetstyle{en-GB}today.

DTMlangsetup[en-GB]{ord=raise} % ,monthyearsep={,space},abbr

DTMsetstyle{en-GB}emph{today} today



canadian:

DTMlangsetup[en-CA]{ord=raise} % ,monthyearsep={,space},abbr  ,ordsep={,}

DTMsetstyle{en-CA}emph{today} today



american:

DTMlangsetup[en-US]{ord=raise} % ,monthyearsep={,space},abbr

DTMsetstyle{en-US}emph{today} today



end{document}

Its result shows you that you can choose the canadian or american variant to get your wished date layout. Because you used italic font in your document I showed in the MWE above italic and normal text for the date.

You can see that in this variant the distance between number and ord is a little bit greater than in your result, but if you want more distance, please uncomment the lines

%usepackage{etoolbox}

%patchcmd{DTMenglishordinal}% <cmd>

%  {#1 DTMenglishfmtordsuffix}% <search>

%  {#1,DTMenglishfmtordsuffix}% <replace>

%  {}{}% <success><failure>

in the MWE above to activate an patch. This patch adds an smal skip , after the number (represented with #1 in the code. Now you get the result:

Okay, now we can include the found code (I choosed american variant) into your code:

documentclass[%

  a4paper,

  10pt,

  demo

]{article}



usepackage[en-US]{datetime2} % <=======================================

DTMlangsetup[en-US]{ord=raise}



usepackage{etoolbox} % <===============================================

patchcmd{DTMenglishordinal}% <cmd> <==================================

  {#1 DTMenglishfmtordsuffix}% <search>

  {#1,DTMenglishfmtordsuffix}% <replace>

  {}{}% <success><failure>



usepackage{pifont} %bouni



usepackage[latin1]{inputenc} %écrire directement les accents et il peut poser des problème

usepackage[T1]{fontenc}



usepackage[colorlinks=true,linkcolor=blue,urlcolor=blue]{hyperref}

usepackage{graphicx}                    % Enable pdflatex

usepackage{wrapfig}

usepackage{amsmath,amsfonts,amsthm}     % Math packages



usepackage{geometry}

geometry{left=2cm,right=2cm,top=1.5cm,bottom=1.5cm}



frenchspacing              % Better looking spacings after periods

usepackage{sectsty}

sectionfont{%                        % Change font of section 

  command % <=================================================== ???????

  usefont{OT1}{phv}{b}{n}%       % bch-b-n: CharterBT-Bold font

  sectionrule{0pt}{0pt}{-5pt}{1pt}}



newcommand{sepspace}{vspace*{1em}}     % Vertical space macro

newcommand{MyName}[1]{ % Name

        Huge usefont{OT1}{phv}{b}{n} hfill #1

        par normalsize normalfont}

newcommand{MySlogan}[1]{ % Slogan}{optional)

    large usefont{OT1}{phv}{m}{n}hfill textit{#1}

    par normalsize normalfont}



pagestyle{empty}           % No pagenumbers/headers/footers





begin{document}



MyName{Name Name}

MySlogan{Curriculum Vitae \ nullhfill  (DTMsetstyle{en-US}today)} % <=======================



sepspace  % Si on ajoute encore sepspace on aura plus d'espace



section*{Informations personelles}



end{document}

with the result:

The red underlined "command" commes from the line I marked in the code with <====== ?????. Is that what you want? If not delete the line with command in the code.