Suppose I have a model:

class SomeModel(models.Model):
   id = models.AutoField(primary_key=True)
   a = models.IntegerField(max_length=10)
   b = models.CharField(max_length=7)

Currently I am using the default admin to create/edit objects of this type. How do I set the field 'a' to have the same number as id? (default=???)

Other question

Suppose I have a model:

   event_date = models.DateTimeField( null=True)
      year = models.IntegerField( null=True)
      month = models.CharField(max_length=50, null=True)
      day = models.IntegerField( null=True)

How can i set the year, month and day fields by default to be the same as event_date field?