llazzaro/django-scheduler

guys please help
i have to compare between 2 data models
STATUS_CHOICES = (
('P', 'Paid'),
('U', 'UNPAID'),
)

class Location(models.Model):
place = models.CharField(max_length=120 , null=True)
def str(self):
return self.place

class Users(models.Model):

    # this function has to compare the date in updated and the date after 30 day 
    # if date in expery is greater than the date in updated >=30 days 
    # status have to change to unpaid 
    # the codes below are not correct of course
    #def now_plus_30(): 
#    return datetime.now() + timedelta(days = 30)
location            = models.ForeignKey(Location , null=True) 
name                = models.CharField(max_length=60)
phone_number    = models.IntegerField(default=0)
price                = models.PositiveIntegerField(blank=True)
status                 = models.CharField(max_length=1, choices=STATUS_CHOICES , default="U")
descrition            = models.TextField(help_text="just to try it with the get_description def")
timestamp            = models.DateTimeField(auto_now_add=True)
updated            = models.DateTimeField(default=now)
    expiry                 = models.DateTimeField(default=now_plus_30())