title: Descriptor 'date' requires a 'datetime.datetime' object but received a 'unicode'
body: <p>I am using piston to write a JSON api for an application I am writing which handles recurring calendar events.</p>
  
  <p>My API was working for regular events, when I attempted to add logic to handle the recurrence, I started getting the following error:</p>
  
  <blockquote>
    <p>descriptor 'date' requires a 'datetime.datetime' object but received a 'unicode'</p>
  </blockquote>
  
  <p>Here is my <code>handlers.py</code>:</p>
  
  <pre><code>from piston.handler import BaseHandler
  from lessons.models import NewEvent, EachEvent
  import calendar
  from datetime import datetime, timedelta
  
  class CalendarHandler(BaseHandler):
  allowed_methods = ('GET',)
  model = EachEvent
  fields = ('actualDate', ('manager', ('firstName', 'lastName')))
  
  def next_date(startDate, recurrence, rangeStart):
      sd = startDate
      while (sd &lt; rangeStart):
          print sd;
          sd += datetime.timedelta(recurrence)
      return sd
  
  def read(self, request, uid, month, year):
      qs = NewEvent.objects.filter(manager__boss = request.user).filter(endDate__gte=datetime.date(year, month, 1)).filter(startDate__lte=datetime.date(year, month, calendar.mdays[month]))
      lessonList = []
      qsList = list(qs)
      for l in qsList:
          if l.frequency == 0:
              x = EachLesson()
              x.lessonID = l.id
              x.actualDate = l.startDate
              x.manager = l.manager
              lessonList.append(x)
          else:
              sd = next_date(l.startDate, l.frequency, datetime.date(year, month, 1))
              while (sd &lt;= datetime.date(year, month, calendar.mdays[month])):
                  x = EachLesson()
                  x.lessonID = l.id
                  x.actualDate = sd
                  x.manager = l.manager
                  lessonList.append(x)
                  sd += datetime.timedelta(recurrence)
  
      return lessonList
  </code></pre>
  
  <p><code>frequency</code> is an IntegerField, <code>actualDate</code>, <code>startDate</code>, and <code>endDate</code> are all DateField.</p>
  
  <p>My URLconf accepts a uid, year, and month, all of which are passed as parameters to the CalendarHandler.read method.</p>