I am using pgfplots to plot the following diagram with monthtly data over 20 years. However, I am not quite satisfied with the labels on the x axis. I'd like to have steps of say 3 years (e.g. 1994, 1997, 2000, 2003, 2006, 2009, 2012). Right now there are steps of 2 years and 3 years.
Can anyone help?

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{width=8cm,compat=newest}
\usepgfplotslibrary{dateplot}
\begin{document}
\begin{figure}[h!]
\begin{center}
\begin{tikzpicture}
\begin{axis}[
width=13cm, height=9cm,
date coordinates in=x,
xticklabel style={/pgf/number format/1000 sep=},
date ZERO=1993-01-01,
xticklabel={\year},
xmin={1993-01-01},
xmax={2013-11-01},
ymin=0.01,
ymax=30,
tick pos=left,
legend pos=outer north east,
legend cell align=left,
]
\addplot table[x=year,y=greece] {data.csv};\addlegendentry{Greece}
\addplot table[x=year,y=portugal] {data.csv};\addlegendentry{Portugal}
\addplot table[x=year,y=ireland] {data.csv};\addlegendentry{Ireland}
\addplot table[x=year,y=italy] {data.csv};\addlegendentry{Italy}
\addplot table[x=year,y=spain] {data.csv};\addlegendentry{Spain}
\addplot table[x=year,y=belgium] {data.csv};\addlegendentry{Belgium}
\addplot table[x=year,y=austria] {data.csv};\addlegendentry{Austria}
\addplot table[x=year,y=france] {data.csv};\addlegendentry{France}
\addplot table[x=year,y=netherlands] {data.csv};\addlegendentry{Netherlands}
\addplot table[x=year,y=germany] {data.csv};\addlegendentry{Germany}
\end{axis}
\end{tikzpicture}
\end{center}
\end{figure}
\end{document}