http://www.java-forums.org/advanced-java/57614-how-plot-line-graph-using-jfreechart-reading-x-y-axis-text-file.html
Type: Posts; User: copeg
http://www.java-forums.org/advanced-java/57614-how-plot-line-graph-using-jfreechart-reading-x-y-axis-text-file.html
I'm not fully clear as to what the requirement is, but if I understand correctly you might want to take a look at the DateAxis class
DateAxis (JFreeChart Class Library (version 1.0.14))