[Matplotlib-users] pytz not installed on Mac

I'm using matplotlib on a Mac. I tried to do a date plot but got an  
error message that pytz is not installed. According to the "using  
matplotlib" tutorial pytz it is supposed to be installed  
automatically...

Traceback (most recent call last):
   File "make_stats.py", line 184, in ?
     do_plot(hosts['ec2'])
   File "make_stats.py", line 80, in do_plot
     from matplotlib.dates import MonthLocator, WeekdayLocator,  
DateFormatter
   File "/Library/Frameworks/Python.framework/Versions/2.4/lib/ 
python2.4/site-packages/matplotlib/dates.py", line 89, in ?
     from pytz import timezone
ImportError: No module named pytz
[simsong@Black s3bandwidth] %

Any cue?