Jinja2 is a templating library that can be used to simplify the process of generating HTML for Python web apps. Django, on the other hand, is a full-fledged MVC framework, which means that it contains libraries for things like database interactions, routing, and caching. Django also includes its own templating library, which works a bit differently than Jinja2. So, the functionality provided by Jinja2 is simply a piece of the functionality that's provided to you by Django. You can actually use Jinja2 to write templates for a Django web application, but it's probably more common to use Jinja2 with more minimalist Python frameworks like Flask (A Python Microframework)

class A:
    created_at = models.DateField

class B:
    created_at = models.DateField

class C:
    created_at = models.DateField
    a = FK