dateformatter doesn't

Greetings. I've been having lots of luck with my date plots. But I've been having a problem getting the dateformatter to work. I'm using the code below. The dates keep getting formatted with the default, "Sep 28 2006" instead of what I want, "Sep 28"

Any thoughts?

from datetime import date,timedelta
from matplotlib.dates import MonthLocator, WeekdayLocator, DateFormatter,MONDAY,SATURDAY
from pylab import *

def dateplot():
     dates = drange(date(2006,10,1),date(2006,12,1),timedelta(days=1))
     vals = 500*(randn(len(dates))+2)

     figure(num=1, figsize=(6.5,4))

     ax = gca() # get the current graphics region

     title(r"Average daily bandwidth")

     ax.xaxis.set_major_formatter(DateFormatter('%b %d'))

     ax.yaxis.set_major_formatter(FormatStrFormatter('%3.0f KBps'))

     plot_date(dates, vals, 'bo')

     # Rotate the labels

     labels = ax.get_xticklabels()