x axis alignment with bar graph

I have some code that produces a series of graphs of data over time. For the most part it works well, but for certain combinations of dates the two plots do not line up, due to the width of the bars in the first subplot. What is the best way for force my second subplot's x axis to be identical to that of the first subplot?


Here is minimal code reproducing the problem:

import matplotlib
from datetime import *
import time
from pylab import *

def toOrd(strDate):
  return datetime(*time.strptime(strDate,"%m/%d/%y")[0:5]).toordinal()

def main():
  startDate = toOrd("05/24/05")
  endDate = toOrd("11/21/06")
  dates = range(startDate,endDate,7)
  axis = subplot(211,axisbelow=True)
  plot_date(dates,dates,visible = False)
  axis.bar(dates,dates, width=3.0)
  axis = subplot(212,axisbelow=True)
  plot_date(dates,dates) #,'-',color = priceColor)

if __name__ == '__main__':