title: Return datetime object of previous month
body: <p>If only timedelta had a month argument in it's constructor.  So what's the simplest way to do this?</p>
  
  <p><b>EDIT:</b> I wasn't thinking too hard about this as was pointed out below.  Really what I wanted was any day in the last month because eventually I'm going to grab the year and month only.  So given a datetime object, what's the simplest way to return <b>any datetime object that falls in the previous month</b>?</p>