\documentclass{article}
\usepackage{fancyhdr}
\pagestyle{fancy}
\usepackage{time}
\newcommand\myTime{\now}
\lhead{\footnotesize\today - \myTime}
\newcommand*{\theto}[1]{%
  \ifnum#1<10 0\fi
  \the#1%
}
\makeatletter
\newcommand*{\timestamp}[1]{%
  \begingroup
    #1
    % format of date: "%d/%02d/%02d "
    \the\day/%
    \theto\month/%
    \expandafter\@gobbletwo\the\year
    \ %
    % format of time: "%02d.%02d"
    \begingroup
      \divide\time by 60 %
      \theto\time.%
      \multiply\time by 60 %
      \edef\x{\endgroup
        \advance\time by -\the\time\relax
      }%
    \x
    \theto\time
  \endgroup
}
\makeatother
\begin{document}
This document was run through \LaTeX{} at \timestamp{\small}.
\end{document}