Note box on calendar

Question

I want to make a calendar with latex and I want to make a box for notes that appears at the end of the calendar to look like this:

I took the template form here Template and I don´t know how to modify a .sty file.

Thank you for reading and if you need mor information let me know and I will edit this post

Edit: I have made some progress by using this new commands:

\newtcolorbox[auto counter,
              number within=chapter,
              list inside=notas
              ]{notas}[1][]{%
    enhanced,
    title={{\begin{minipage}{0.99\linewidth}\textbf{\textit{#1}}\end{minipage}}},
    ,
    halign title=left,
    sharp corners,
    colback=white,
    coltitle=black,
    colbacktitle=white,
    boxrule=0pt,frame hidden,
    overlay unbroken={%
      \draw[black,double] (interior.north west)--(interior.south west);%
      },
    boxed title style={%
      colframe=white, 
      boxrule=0pt,
      colback=white,
      left=0pt,
      right=0pt},
    attach boxed title to top left={xshift={-5pt}},
}

\def\daysep{\vskip2pt\hrule\vskip4pt}

\def\timesep{\vskip6pt}

Using it like this outside the calendar enviroment:

\begin{notas}[Notas]
\textbf{12:30-14:30} \daysep Física cuántica I \timesep \textbf{12:30-14:30} \daysep Física cuántica I \timesep
\end{notas}

Providing:

But I still can't figure it out how to make them appear in columns like the draw I made

Answer 1

One way using the multicol package. The calendar part is not relevant to the issue, so it is omitted in the MWE:

\documentclass[a4paper]{article}
%\usepackage[margin=2cm]{geometry}
\usepackage[spanish]{babel}
\usepackage{multicol}
\usepackage{microtype}

\newcommand\nota[1]{\par\bigskip\noindent{\bfseries #1\smallskip\hrule\smallskip\noindent}\par}

\begin{document}

%\begin{calendar}
%\end{calendar}

\noindent
\fboxsep1em
\fboxrule2pt
\fbox{\parindent0pt\footnotesize\sffamily
\noindent\begin{minipage}{\dimexpr\linewidth-2\fboxsep-2\fboxrulewidth}
{\bfseries\large Notas:}\\[-2.5em] 
\begin{multicols}{5}\raggedright
\nota{Lunes} Ir al cine.
\nota{7:00} Grabar la peli de la tele.
\nota{}Call Of Dutty (Pablito \& Co.  revenge).\newcolumn
\nota{Martes} Ver la peli que grabé ayer. 
\nota{Martes tarde} Ir al teatro.
\nota{Martes noche} Ir otra vez al teatro. \newcolumn
\nota{Miércoles} Descanso de media semana.\newcolumn
\nota{Jueves} Escuchar música.
\nota{} Call of Duty.
\nota{} Escuchar música.
\nota{5:00 PM} Curso de Procastinación Avanzado.
\newcolumn
\nota{Viernes} Descansar (tanto trabajar no es bueno).
\end{multicols}
\end{minipage}}
\end{document}