% !TEX encoding = utf-8
% !TEX program = xelatex

\documentclass[12pt,a4paper]{article}

% We use the multilingual typesetting (French language by default)
\usepackage{polyglossia}
\setdefaultlanguage{french}
\PolyglossiaSetup{french}{indentfirst=false}

% We re-define margin
\usepackage{geometry}
\geometry{hmargin=2.5cm, vmargin=1.5cm}

\usepackage{fontspec}

\newcount\nextyear
\nextyear \year\relax % Initialize
\advance\nextyear 1\relax % Increase

\pagestyle{headings}

\begin{document}

Bonjour le monde\footnote{Le fameux \textit{Hello World} !} ! Voilà une agréable journée.

Nous sommes en \the\year{} rendez-vous en \the\nextyear.

\end{document}