title: Exception was: unsupported operand type(s) for -: 'str' and 'datetime.timedelta'
body: <p>I am new with python and I am making a system that deals with request.GET method... 
  when i pass a date to the system, if it is exist then it will look for the database and show data according to that date and other dates, else it will display a date with other date...
  here is my code :</p>
  
  <pre><code>from django.utils.xmlutils import SimplerXMLGenerator
  from piston.handler import BaseHandler
  from booking.models import *
  from django.db.models import *
  from piston.utils import rc, require_mime, require_extended, validate
  import datetime
  
  class BookingHandler(BaseHandler):
      allowed_method = ('GET', 'POST', 'PUT', 'DELETE')
      fields = ('id', 'date_select', 'product_name', 'quantity', 'price','totalcost', 'first_name', 'last_name', 'contact', 'product')
      model = Booking
      #for product availability
      def read(self, request, id, date_select):
          if not self.has_model():
              return rc.NOT_IMPLEMENTED
          try:   
              prod = Product.objects.get(id=id)
              merge = []
              checkDateExist = Booking.objects.filter(date_select=date_select)
              if checkDateExist.exists():
                  entered_date = Booking.objects.values('date_select').distinct('date_select').filter(date_select=date_select)[0]['date_select']
              else:             
                  enteredTemp_date = datetime.datetime.strptime(date_select, '%Y-%m-%d')
                  entered_date = datetime.datetime.strftime(enteredTemp_date,'%Y-%m-%d')
  
  
              delta = datetime.timedelta(days=3)
              target_date = entered_date - delta
              day = 1
              for x in range(0,5):
                  delta = datetime.timedelta(days=x+day)
                  new_date = target_date + delta
                  maximumProdQuantity = prod.quantity
                  quantityReserve = Booking.objects.filter(date_select=new_date, product=prod).aggregate(Sum('quantity'))['quantity__sum']
                  if quantityReserve == None:
                      quantityReserve = 0
  
                  data1 = {'maximum_guest': maximumProdQuantity, 'avialable': quantityReserve, 'date': new_date}
                  merge.append(data1)    
  
              return merge       
          except self.model.DoesNotExist:
              return rc.NOT_HERE 
  </code></pre>
  
  <p>and i got this error :</p>
  
  <pre><code>Piston/0.3dev (Django 1.3.1) crash report:
  
  Method signature does not match.
  
  Signature should be: id, date_select
  
  Exception was: unsupported operand type(s) for -: 'str' and 'datetime.timedelta'
  </code></pre>
  
  <p>i think in my <code>else</code> statement the <code>entered_date</code> become a string, i do this line <code>entered_date = datetime.datetime.strftime(enteredTemp_date,'%Y-%m-%d')</code> so that the date format will be not <code>2011-12-01 00:00:00</code> i just only need <code>2011-12-01</code>. my question is how can i get <code>2011-12-01</code> that is datetime format not a string?
  can anyone can give a hint or an idea about my case?
  thanks</p>