\documentclass[fontsize=20pt]{scrartcl}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[margin=1cm,a4paper,landscape]{geometry}
\pagestyle{empty}
\usepackage{graphicx}
\usepackage{tikz}
\usepackage{verbatim}
\begin{comment}
:Title: Birthday calendar
:Tags: Calendar library;Calendars
:Author: Hakon Malmedal
:Slug: birthday-calendar
\end{comment}
\usetikzlibrary{calendar,fit}
\usepackage{expl3,xparse}

%% Adapted from http://tex.stackexchange.com/a/10199/4771
\makeatletter%
\tikzoption{day headings}{\tikzstyle{day heading}=[#1]}
\tikzstyle{day heading}=[]
\tikzstyle{day letter headings}=[
    execute before day scope={ \ifdate{day of month=1}{%
      \pgfmathsetlength{\pgf@ya}{\tikz@lib@cal@yshift}%
      \pgfmathsetlength\pgf@xa{\tikz@lib@cal@xshift}%
      \pgftransformyshift{-\pgf@ya}
      \foreach \d/\l in {0/Monday,1/Tuesday,2/Wednesday,3/Thursday,%
                         4/Friday,5/Saturday,6/Sunday} {
        \pgf@xa=\d\pgf@xa%
        \pgftransformxshift{\pgf@xa-\cellwidth/2}%
        \pgftransformyshift{\pgf@ya}%
        \node[above=-0.5ex,day heading]{\l};%
      }
    }{}%
  }%
]
\makeatother%
%% End

% Not necessary for english
% Adapted from pgf source
%\def\pgfcalendarmonthname#1{%
  %\translate{\ifcase#1\or January\or February\or March\or April\or
    %May\or June\or July\or August\or September\or Oktober\or
    %November\or Desember\fi}%
%}

\makeatletter
\tikzstyle{month label above centered}=[%
  execute before day scope={%
    \ifdate{day of month=1}{%
      {
        \pgfmathsetlength{\pgf@xa}{\tikz@lib@cal@xshift}%
        \pgf@xb=\tikz@lib@cal@width\pgf@xa%
        \advance\pgf@xb by-\pgf@xa%
        \pgf@xb=.5\pgf@xb%
        \pgftransformxshift{\pgf@xb}%
        \pgftransformxshift{-\cellwidth/2}%
        \pgfmathsetlength{\pgf@y}{\tikz@lib@cal@yshift}%
        \pgftransformyshift{0.333\pgf@y}
        \tikzmonthcode%
      }
    }{}},
  every month/.append style={anchor=base}
]
\makeatother
%% End

\ExplSyntaxOn

%% Adapted from http://tex.stackexchange.com/a/56214/4771
%%
% first of all we define the user level commands
\NewDocumentCommand{\addtext}{ m }{ \bdaycal_input_add:n { #1 } }
\NewDocumentCommand{\addtextyear}{ mm }{ \bdaycal_input_add_y:nn { #1 } { #2 } }
\NewDocumentCommand{\showtext}{ }{ \bdaycal_output_direct: }

% allocate variable:
% a sequence for global storage of the inputs;
\seq_new:N \g_bdaycal_input_seq

% store globally an input in the sequence
\cs_new:Npn \bdaycal_input_add:n #1
 {
  \seq_gput_right:Nn \g_bdaycal_input_seq { #1 }
 }

\cs_new:Npn \bdaycal_input_add_y:nn #1 #2
 {
  \seq_gput_right:Nn \g_bdaycal_input_seq { #1 ~ ( \int_to_arabic:n
    { \pgfcalendarifdateyear - #2 } ) }
 }

% how to output in direct order; we simply do a mapping function calling
% \bdaycal_print:n after incrementing the counter
\cs_new_protected:Npn \bdaycal_output_direct:
 {
  \seq_map_inline:Nn \g_bdaycal_input_seq
   {
    \bdaycal_print:n { ##1 }
   }
  \seq_gclear:N \g_bdaycal_input_seq
 }

% the printing macro; change here for adapting to your wishes
\cs_new:Npn \bdaycal_print:n #1
 {
  #1 \par
 }
%% End

%%% Knuth's AoCP, vol 1, 2nd ed, pp 155--156
%\int_new:N \l_easter_Y_int
%\int_new:N \l_easter_G_int
%\int_new:N \l_easter_C_int
%\int_new:N \l_easter_X_int
%\int_new:N \l_easter_Z_int
%\int_new:N \l_easter_D_int
%\int_new:N \l_easter_E_int
%\int_new:N \l_easter_N_int
%\int_new:N \l_easter_M_int
%\int_new:N \l_easter_julian_day_int

%\cs_new:Nn \easter_sunday:n {

  %\int_set:Nn \l_easter_Y_int { #1 }

  %\int_set:Nn \l_easter_G_int {
    %\int_mod:nn { \l_easter_Y_int } { 19 } + 1
  %}

  %\int_set:Nn \l_easter_C_int {
    %\int_div_truncate:nn { \l_easter_Y_int } { 100 } + 1
  %}

  %\int_set:Nn \l_easter_X_int {
    %\int_div_truncate:nn { 3 * \l_easter_C_int } { 4 } - 12
  %}

  %\int_set:Nn \l_easter_Z_int {
    %\int_div_truncate:nn { 8 * \l_easter_C_int + 5 } { 25 } - 5
  %}

  %\int_set:Nn \l_easter_D_int {
    %\int_div_truncate:nn { 5 * \l_easter_Y_int } { 4 } - \l_easter_X_int - 10
  %}

  %\int_set:Nn \l_easter_E_int {
    %\int_mod:nn { 11 * \l_easter_G_int + 20 + \l_easter_Z_int
      %- \l_easter_X_int } { 30 }
  %}

  %% \int_mod:nn behaves strangely.
  %\int_compare:nNnT { \l_easter_E_int } < { 0 }
  %{
    %\int_add:Nn \l_easter_E_int { 30 }
  %}

  %\int_compare:nNnTF { \l_easter_E_int } = { 25 }
  %{ % true
    %\int_compare:nNnT { \l_easter_G_int } > { 11 }
    %{ % true
      %\int_incr:N \l_easter_E_int
    %}
  %}
  %{ % false
    %\int_compare:nNnT { \l_easter_E_int } = { 24 }
    %{ % true
      %\int_incr:N \l_easter_E_int
    %}
  %}

  %\int_set:Nn \l_easter_N_int { 44 - \l_easter_E_int }

  %\int_compare:nNnT { \l_easter_N_int } < { 21 }
  %{ % true
    %\int_add:Nn \l_easter_N_int { 30 }
  %}

  %\int_add:Nn \l_easter_N_int {
    %7 - \int_mod:nn { \l_easter_D_int + \l_easter_N_int } { 7 }
  %}

  %\int_compare:nNnTF { \l_easter_N_int } > { 31 }
  %{ % true
    %\int_sub:Nn \l_easter_N_int { 31 }
    %\int_set:Nn \l_easter_M_int { 4 } % April
  %}
  %{ % false
    %\int_set:Nn \l_easter_M_int { 3 } % March
  %}

  %\pgfcalendardatetojulian { \l_easter_Y_int -
     %\l_easter_M_int - \l_easter_N_int
  %} { \l_easter_julian_day_int }

%}

%\pgfkeys{/pgf/calendar/Easter/.default = 0}
%\pgfkeys{/pgf/calendar/Easter/.code =
  %{
    %\easter_sunday:n { \pgfcalendarifdateyear }
    %\int_compare:nNnT { \pgfcalendarifdatejulian }
    %=  {\l_easter_julian_day_int + #1}
    %{ \pgfcalendarmatchestrue }
  %}
%}

%\int_new:N \l_advent_Y_int
%\int_new:N \l_advent_xmas_julian_day_int
%\int_new:N \l_advent_xmas_week_day_int
%\int_new:N \l_advent_julian_day_int

%\cs_new:Nn \advent_sunday:n {

  %\int_set:Nn \l_advent_Y_int { #1 }

  %\pgfcalendardatetojulian { \l_advent_Y_int - 12 - 25 } {
    %\l_advent_xmas_julian_day_int }

  %\pgfcalendarjuliantoweekday { \l_advent_xmas_julian_day_int } {
    %\l_advent_xmas_week_day_int }

  %\int_set:Nn \l_advent_julian_day_int {
    %\l_advent_xmas_julian_day_int - \l_advent_xmas_week_day_int - 22 }

%}

%\pgfkeys{/pgf/calendar/Advent/.default = 0}
%\pgfkeys{/pgf/calendar/Advent/.code =
  %{
    %\advent_sunday:n { \pgfcalendarifdateyear }
    %\int_compare:nNnT { \pgfcalendarifdatejulian }
    %=  {\l_advent_julian_day_int + #1}
    %{ \pgfcalendarmatchestrue }
  %}
%}

%% http://www.tondering.dk/claus/cal/week.php#calcweekno
\int_new:N \l_week_number_year_int
\int_new:N \l_week_number_month_int
\int_new:N \l_week_number_day_int
\int_new:N \l_week_number_a_int
\int_new:N \l_week_number_b_int
\int_new:N \l_week_number_c_int
\int_new:N \l_week_number_s_int
\int_new:N \l_week_number_e_int
\int_new:N \l_week_number_f_int
\int_new:N \l_week_number_g_int
\int_new:N \l_week_number_d_int
\int_new:N \l_week_number_n_int
\int_new:N \l_week_number_W_int

\cs_new:Nn \week_number:nnn {

  \int_set:Nn \l_week_number_year_int { #1 }
  \int_set:Nn \l_week_number_month_int { #2 }
  \int_set:Nn \l_week_number_day_int { #3 }

  \int_compare:nNnTF { \l_week_number_month_int } < { 3 } % jan or feb
  { % true

    \int_set:Nn \l_week_number_a_int { \l_week_number_year_int - 1 }

    \int_set:Nn \l_week_number_b_int {
      \int_div_truncate:nn { \l_week_number_a_int } { 4 }
      - \int_div_truncate:nn { \l_week_number_a_int } { 100 }
      + \int_div_truncate:nn { \l_week_number_a_int } { 400 }
    }

    \int_set:Nn \l_week_number_c_int {
      \int_div_truncate:nn { \l_week_number_a_int - 1 } { 4 }
      - \int_div_truncate:nn { \l_week_number_a_int - 1 } { 100 }
      + \int_div_truncate:nn { \l_week_number_a_int - 1 } { 400 }
    }

    \int_set:Nn \l_week_number_s_int {
      \l_week_number_b_int - \l_week_number_c_int }

    \int_zero:N \l_week_number_e_int

    \int_set:Nn \l_week_number_f_int { \l_week_number_day_int - 1
      + 31 * ( \l_week_number_month_int - 1 ) }

  } % end true
  { % false

    \int_set_eq:NN \l_week_number_a_int \l_week_number_year_int

    \int_set:Nn \l_week_number_b_int {
      \int_div_truncate:nn { \l_week_number_a_int } { 4 }
      - \int_div_truncate:nn { \l_week_number_a_int } { 100 }
      + \int_div_truncate:nn { \l_week_number_a_int } { 400 }
    }

    \int_set:Nn \l_week_number_c_int {
      \int_div_truncate:nn { \l_week_number_a_int - 1 } { 4 }
      - \int_div_truncate:nn { \l_week_number_a_int - 1 } { 100 }
      + \int_div_truncate:nn { \l_week_number_a_int - 1 } { 400 }
    }

    \int_set:Nn \l_week_number_s_int {
      \l_week_number_b_int - \l_week_number_c_int }

    \int_set:Nn \l_week_number_e_int { \l_week_number_s_int + 1 }

    \int_set:Nn \l_week_number_f_int { \l_week_number_day_int
      + \int_div_truncate:nn {
        153 * ( \l_week_number_month_int - 3 ) + 2 } { 5 }
      + 58 + \l_week_number_s_int }

  } % end false

  \int_set:Nn \l_week_number_g_int {
    \int_mod:nn { \l_week_number_a_int + \l_week_number_b_int } { 7 }  }

  \int_set:Nn \l_week_number_d_int {
    \int_mod:nn { \l_week_number_f_int + \l_week_number_g_int
      - \l_week_number_e_int } { 7 }  }

  \int_set:Nn \l_week_number_n_int {
    \l_week_number_f_int + 3 - \l_week_number_d_int }

  \int_compare:nNnTF { \l_week_number_n_int } < { 0 }
  { %true

    \int_set:Nn \l_week_number_W_int { 53
      - \int_div_truncate:nn { \l_week_number_g_int
        - \l_week_number_s_int } { 5 } }

  } % end true
  { % false

    \int_compare:nNnTF { \l_week_number_n_int } > { 364
      + \l_week_number_s_int }
    { % true

      \int_set:Nn \l_week_number_W_int { 1 }

    } % end true
    { % false

      \int_set:Nn \l_week_number_W_int { \int_div_truncate:nn {
          \l_week_number_n_int } { 7 } + 1 }

    } % end false

  } % end false

}

\definecolor{roed}{rgb}{0.937254901961,0.16862745098,0.176470588235}
\definecolor{blaa}{rgb}{0,0.156862745098,0.407843137255}

\newsavebox{\flagNO}
%\savebox{\flagNO}{
%\begin{tikzpicture}
  %\fill[roed] rectangle (6pt,6pt);
  %\fill[roed,yshift=10pt] rectangle (6pt,6pt);
  %\fill[roed,xshift=10pt] rectangle (12pt,6pt);
  %\fill[roed,xshift=10pt,yshift=10pt] rectangle (12pt,6pt);
  %\fill[blaa,yshift=7pt] rectangle (22pt,2pt);
  %\fill[blaa,xshift=7pt] rectangle (2pt,16pt);
%\end{tikzpicture}
%}

\pgfkeys{/tikz/week~number/.code =
  {
    \week_number:nnn { 
      \pgfcalendarifdateyear } { 
      \pgfcalendarifdatemonth } { 
      \pgfcalendarifdateday }
    \addtext{ KW ~ \int_to_arabic:n { \l_week_number_W_int } }
  }
}

\ExplSyntaxOff

%\pgfkeys{/tikz/flag-flying day/.code =
  %{
    %\draw (-\cellwidth,0) node [above right,font=\Huge]
    %{\resizebox{!}{0.8ex}{\usebox{\flagNO}}};
  %}
%}

\pgfkeys{/tikz/observance/.code =
  {
    \addtext{#1}
  }
}

\pgfkeys{/tikz/anniversary/.code 2 args=\addtextyear{#1}{#2}}

\pgfkeys{/tikz/day code =
  {
    \node (lower right) at (0,0) [above left,font=\Huge] {\tikzdaytext};
    \node (upper left) at (-\cellwidth,\cellheight)
    [below right,align=left,text width=\cellwidth-\pgflinewidth,
    font=\tiny,black] {\showtext};
    \node (lower left) at (-\cellwidth,0) {};
    \node[rounded corners, draw,
          fit=(lower right) (upper left) (lower left),
          inner sep=1mm] {};
  }
}

\pgfkeys{/tikz/inner sep = 0pt}

\pgfkeys{/tikz/day xshift=\cellwidth+2mm+2mm}

\pgfkeys{/tikz/day yshift=\cellheight+2mm+2mm}

\newlength{\cellheight}
\setlength{\cellheight}{25mm}
\newlength{\cellwidth}
\setlength{\cellwidth}{35mm}

\begin{document}

\centering

\input{gcal_out.tex}

\end{document}
