\listfiles

\documentclass{article}
\usepackage{datetime}
\usepackage[english]{datenumber}
\begin{document}
\section{Package datenumber}
\begin{itemize}
  \item \setdate{2015}{1}{21}
    \datedate
  \item \setdate{2015}{1}{22}
    \datedate
  \item \setdate{2015}{1}{23}
    \datedate
  \item \setdate{2015}{1}{31}
    \datedate
\end{itemize}

\section{Package datetime}
\begin{itemize}
\item \newdate{21}{21}{1}{2015}
  \displaydate{21}
\item \newdate{22}{22}{1}{2015}
  \displaydate{22}
\item \newdate{23}{23}{1}{2015}
  \displaydate{23}
\item \newdate{31}{31}{1}{2015}
  \displaydate{31}
\end{itemize}
\end{document}
