Fetch the schedules for the given rooms.

def fetch_todays_schedule(self, rooms):
        """ Fetch the schedules for the given rooms. """
        def _format_date(d):
            return d.strftime('%Y/%m/%d')
        room_ids = self.fetch_room_ids(rooms)
        ret = {}
        now = datetime.datetime.now()
        nowStr = _format_date(now)
        tomorrowStr = _format_date(now + datetime.timedelta(days=1))
        for room_name in room_ids:
            ret[room_name] = []
            events = json.loads(self.open_url(
                            "timetables/%s?startDate=%s&endDate=%s" % (
                                room_ids[room_name], nowStr, tomorrowStr)))
            for event in events:
                starttime = datetime.datetime.fromtimestamp(
                            event['startDate']/1000.0)
                endtime = datetime.datetime.fromtimestamp(
                            event['endDate']/1000.0)
                description = event['activityDescription']
                if description is None:
                    description = event['notes']
                if description is None:
                    description = '( geen omschrijving )'
                ret[room_name].append((starttime,
                                       endtime,
                                       normalize_event_name(description)))
        return ret