Problem with 0.85 package for ubuntu

Using the 0.85 package for ubuntu, I get the following error
when I run my application:

?

from matplotlib.dates import date2num,

num2date, DateFormatter, IndexDateFormatter

File
“/home/jdhunter/debs/matplotlib/usr/lib/python2.4/site-packages/matplotlib/dates.py”,
line 88, in ?

ImportError: No module named pytz

Any ideas?

Thanks,

VJ