Pour l'année, il faut modifier la valeur de `\year` (qui contient manifestement l'année courante). Pour le reste, il faut modifier le calcul de `\mycount`, voir ci-dessous.
\documentclass[french]{article}
\usepackage[T1]{fontenc}
\usepackage{tikz}
%%%<
\usepackage{verbatim}
\usepackage[french]{translator}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{5pt}%
%%%>
\begin{comment}
:Title: A calendar of circles
:Tags: Foreach
:Author: Till Tantau
:Slug: calendar-circles
A calendar example from the PGF manual. Modifications are
- changes in font family and size commands
- shaded background circle
- shaded month circles
- font sizes and distances.
\end{comment}
\usetikzlibrary{calendar,shadings}
\renewcommand*{\familydefault}{\sfdefault}
\colorlet{winter}{blue}
\colorlet{spring}{green!60!black}
\colorlet{summer}{orange}
\colorlet{fall}{red}
% A counter, since TikZ is not clever enough (yet) to handle
% arbitrary angle systems.
\newcount\mycount
% ===============================================================
% ================ Change start =================================
% ===============================================================
\year=2019
% ===============================================================
% ================ Change end ===================================
% ===============================================================
\usepackage{babel}
\begin{document}
\begin{tikzpicture}[transform shape,
every day/.style={anchor=mid,font=\tiny}]
\node[circle,shading=radial,outer color=blue!30,inner color=white,
minimum width=15cm] {\textcolor{blue!80!black}{\Huge2019}};
{\textcolor{blue!80!black}{\Huge\the\year}};
\foreach \month/\monthcolor in
{1/winter,2/winter,3/spring,4/spring,5/spring,6/summer,
7/summer,8/summer,9/fall,10/fall,11/fall,12/winter} {
% Computer angle:
\mycount=\month
\advance\mycount by -1
% ===============================================================
% ================ Change start =================================
% ===============================================================
\multiply\mycount by -30
\advance\mycount by 90
% ===============================================================
% ================ Change end ===================================
% ===============================================================
\shadedraw[shading=radial,outer color=\monthcolor!30,middle color=white,
inner color=white,draw=none] (\the\mycount:5.4cm) circle(1.4cm);
% The actual calendar
\calendar at (\the\mycount:5.4cm) [
dates=2019-\month-01 dates=\the\year-\month-01 to 2019-\month-last]
\the\year-\month-last]
if (day of month=1) {\large\color{\monthcolor!50!black}\tikzmonthcode}
if (Sunday) [red]
if (all) {
% Again, compute angle
\mycount=1
\advance\mycount by -\pgfcalendarcurrentday
\multiply\mycount by 11
\advance\mycount by 90
\pgftransformshift{\pgfpointpolar{\mycount}{1.2cm}}};}
\end{tikzpicture}
\end{document}
