from celery.task import periodic_task
from celery.schedules import crontab

@periodic_task(ignore_result=True, run_every=crontab(minute=0,hour=0,day_of_week='saturday'))  # every minute
def just_print():
    print "Print from celery task"

class Task(models.Model):
    start_time = models.TimeField()
    weekday= models.CharField()
    start = models.DateTimeField()

    def __unicode__(self):
        return "%s %s" % (self.start_time, self.end_time)

    def save(self, *args, **kwargs):
       just_print.run_every=crontab(minute=self.start_time.minute,hour=self.start_time.hour,day_of_week=self.weekday)
just_print.apply_async(eta=(start))