Auto-populating created_by and actionDate field with Django admin site

I have a model like this:

class Tour(models.Model):
   Name=models.CharField(max_length=100)
   Count=models.SmallIntegerField() 
   ActionDate=models.DateTimeField(editable=False)
   ActionUser=models.ForeignKey(User,editable=False)
   StatusType=models.ForeignKey(StatusType)

now I wanna auto populate current user in my Tour,so I used this code in admin.py:

 def save_model(self, request, obj, form, change): 
      instance = form.save(commit=False)
      instance.ActionUser = request.user
      instance.save()
      form.save_m2m()
      return instance

admin.site.register(Tour,TourAdmin)

it work great and it auto polulate current User in my Tour Table,but now I can't save current date in ActionDate field,I added this code to save_model but it cause error:

self.ActionDate=datetime.datetime.today()

then I 开发者_如何学运维tryed to override save in my Tour Model :

def save(self,*args,**kwargs):
      self.ActionDate=datetime.datetime.today()
      super(Tour, self).save(*args,**kwargs)

but this cause error,too. what should I do to auto populate both ActionUser and ActionDate? tnx in advance

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Why don't you use auto_now in the field definition?