Design a custom calendar: advise?

Question

I would like to design with LaTeX a calendar that would look like this:

I would like to have some advise about how to draw the frames and how to put some text (or tabular formatted text) in it? I am not a TikZ user but I am ready to learn a little bit of it (if it is the best solution).

As about how to compute the dates, etc. it is not a problem at all since I plan to maybe use Python to generate the LaTeX code.

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PS:

Since I might use Python to generate the code, I don't think I would need any already existing library that manages calendar. So, this question is more about how to draw a canvas as in the picture above.

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My first attempt

I did

\documentclass[landscape]{article}
\usepackage[table,xcdraw]{xcolor}
\usepackage{amsfonts}
\usepackage{tabularx}
\usepackage{wasysym}
%%%%%%%%%%
% Layout %
%%%%%%%%%%
\def\myHMargin{1cm}
\def\myVMargin{1cm}
\usepackage[hmargin={\myHMargin,\myHMargin},
            vmargin={\myVMargin,\myVMargin}]{geometry}
\def \x
{\small
\begin{tabular}{@{} >{\centering\let\newline\ \arraybackslash\hspace{1pt}}m{3.5cm} <{\hspace*{1mm}} }
\cellcolor[HTML]{C0C0C0}{}\[-3mm]
{\cellcolor[HTML]{C0C0C0}{\color[HTML]{000000} \footnotesize $, \mathbf{{100}}$ \hfill {\footnotesize25 juin}}} \[1.5mm]
\hfill $\times \hspace{-1pt}\approx\hspace{-1pt}\checked$ \

\dotfill $\square$,$\square$,$\square$ \
\dotfill $\square$,$\square$,$\square$ \
\dotfill $\square$,$\square$,$\square$ \
\dotfill $\square$,$\square$,$\square$ \[1mm]
\end{tabular}}
\begin{document}
\setlength{\tabcolsep}{0pt}
\begin{tabular}{|c|c|c|c|c|c|c|}
\hline
lundi & mardi & mercredi & jeudi & vendredi & samedi & dimanche \
\hline
\[3mm]
\hline
\x & \x & \x& \x & \x & \x& \x\
\hline
\x & \x & \x& \x & \x & \x& \x\
\hline
\x & \x & \x& \x & \x & \x& \x\
\hline
\end{tabular}
\end{document}

I'm pretty satisfied with the result but there is a still a problem with rule (see picture below).

Feel free to make my coder better.