What is the difference between `auto_now_add` and `timezone.now` (as default value) for models in Django?
Example:

```py
create_date = models.DateTimeField(auto_now_add=True)

```

and

```py
create_date = models.DateTimeField(default=timezone.now)

```

?

**UPD.** I'm talking about the case when I always not overriding default value.