bug field with auto_now_add=True not showing for admin


    loggoff = models.DateTimeField(null=True, blank=True,auto_now_add=True)
    readonly_fields =  ('loggoff',) 

I found some setup but nothing work i need to change false to true and back to false to see my record  

```my admin setting
```from django.contrib import admin
from .models import Loginusers_log ,Logoutusers_log
class Loginusers_log(admin.ModelAdmin):
    fields= [
    readonly_fields= ['loggoff', 'usernamel',]

    class Meta:
        model= Loginusers_log

Correct - see the first Note box in the docs for auto_now_add

I have fix it now , login and logout time too . next level are more difficult

in model

  loggoff = models.DateTimeField(null=True, blank=True,auto_now_add=False)

and i use filter for update