Using shortcut with argument in tcolorbox

I want to do something like this:

\documentclass{article}
\usepackage[ngerman]{isodate} %for printing the date
\usepackage[dvipsnames]{xcolor} %for color names
\usepackage{tcolorbox}
\usepackage{lipsum}

\newcommand{\MyArgument}{Datum: \printdate{#1}}

\newtcolorbox{MyBox1}[1]{colback=red!5!white, colframe=red!75!black, title=\MyArgument }

%some more "\newtcolorbox{...}" with different colors, but all with title=\MyArgument

\begin{document}

\begin{MyBox}{2014-02-11}
\lipsum
\end{MyBox}

\end{document}


The output should be a box with the title "Datum: 11. Februar 2014" (German date format)

The purpose is that I want to be able to change the title of all boxes at the same time. How can I do that?

-
Providing a compilable example that begins with \documentclass is extremely helpful to those who wish to help you. – Steven B. Segletes Feb 11 '14 at 13:41
Thanks, I added it now. A also changed the date format to German because this led to some confusion. – MaxD Feb 11 '14 at 17:27

Not sure if this is what you want:

\documentclass[dvipsnames]{article}
\usepackage{tcolorbox}
\usepackage[english]{isodate} %for printig the date
\usepackage{lipsum}

\newcommand\MyCom[1]{Datum:~\numdate{#1}}

\newtcolorbox{MyBoxi}[1]{
colback=red!5!white,
colframe=red!75!black,
title=\MyCom{#1}
}
\newtcolorbox{MyBoxii}[1]{
colback=cyan!5!white,
colframe=cyan!75!black,
title=\MyCom{#1}
}

\begin{document}

\begin{MyBoxi}{2014-02-11}
\lipsum[4]
\end{MyBoxi}

\begin{MyBoxii}{2014-02-11}
\lipsum[4]
\end{MyBoxii}

\end{document}


-
I suggest \usepackage[german]{isodate} and \newcommand\MyCom[1]{Datum:~\numdate\printdate{#1}} – Steven B. Segletes Feb 11 '14 at 13:57
@StevenB.Segletes suggestion accepted :-) – Gonzalo Medina Feb 11 '14 at 14:30
The \numdate gives the date as 11.02.2014 instead of 11. Februar 2014, as requested by the OP. – Steven B. Segletes Feb 11 '14 at 14:36
@StevenB.Segletes I am not sure whether the OP is also asking for a way to change the date format. I'll use your suggestion for \numdate as well. Thanks. – Gonzalo Medina Feb 11 '14 at 15:17
@GonzaloMedina Sorry for the confusing formulation! This seems to be the essential part I was asking for: \makeatletter \def\iso@isodash{mmmmm} \makeatother Can you explain what it does? – MaxD Feb 11 '14 at 17:01