Plotting data against date/time


a newbie question.
After having a look at the date examples of matplotlib, I still have
some problem with this:
I have data starting at a certain date/time (e.g. 30 Nov 2006 12.00
pm). I have one data for every hour starting from the 13th hour after
the starting time until the 96th hour.
I would like to put on the x axis the day/hour (let's say every 3 or 6 hour).

Could you please help me setting me on the right way to the solution?