How can properly verify a user is 18 or older in django?

Question

I want to validate whether a user's age (birth_date) is 18+, this is my current code though it isn't working:

...
def min_date():
    return (date.today() - timedelta(days=6570))

class User(BaseModel, RemovabledModel, AbstractUser):
 birth_date = models.DateField(
        verbose_name=_('birth date'),
        help_text=_('Birth date'),
        null=True,
        blank=True,
        validators=[
            MinValueValidator(
                limit_value=min_date(),
                message=("User must be 18 or older")
            ),
        ]
    )

This runs and is functional, but I can still set a user's age to today's date without the application throwing any error message like it would with other validators.

Edit: In case it is relevant, this is related validator:

def min_date(): 
    return (date.today() - timedelta(days=6570)) 

class SignUpSerializer(serializers.Serializer): 
    birth_date = serializers.DateField( 
        write_only=True, 
        required=True, 
        validators=[ 
            MinValueValidator( 
                limit_value=min_date(), 
                message=("User must be 18 or older") ),
        ] 
    )

Answer 1

You can fix the validation on the model like so (This also means you can omit the custom field from your serializer):

def min_date():
    return (date.today() - timedelta(days=6570))

class User(BaseModel, RemovabledModel, AbstractUser):
 birth_date = models.DateField(
        verbose_name=_('birth date'),
        help_text=_('Birth date'),
        null=True,
        blank=True,
    )
    def clean(self):
        super().clean()
        if self.birth_date > min_date():
             # raise validation error here             

Relevant documentation
Custom User Model

How it's currently set up on the model:

On the date field in the User model; you are calling the min_date() function inside the validator, say you were to migrate.
You head off for the day.
Then the next day; you get back to development; you makemigrations, migrate; and it should say no changes made, but there is a change to the date field.
The date inside the min_date function will be incremented.

The migration doesn't know you are calling a function in this case; it just sees the value.