How much effort went into the creation of django and its features?

Programming is, in many ways, leeching off of the effort of another - why build your own library to do some task when someone else already made one for you? Django seems to be a good example of such a thing - its features are various and multifaceted, and though this course just scratches the surface it's already apparent that it makes everything much easier, especially the Admin page. However, while we the student web developers can simply use Django and not worry about where it came from, the fact remains that some person or group had to put this thing together. I am curious - how much time and effort had to go into the creation of the Django web framework? What sorts of complexities happen behind the scenes that are hidden (or simply irrelevant) to us? And when, in the future, Django will be needing an update or replacement, how much experience is necessary to do such a thing?