My cat enjoys going outdoors. I try to keep her in but sometimes she
slips out when the door is open or she pushes out a screen. In any
case when she goes outside she just takes off walking down the street
and is gone for hours. Then, every night around 7pm she is meowing
loudly at the front door.

How on earth does the cat find its way to the house after going far
away? But more precisely, does a cat actually understand in its mind
that a particular structure is its home where food/water/safety is?
All the houses look alike on my street, and yet the cat is at my front
door. And further does a cat in its mind understand that it must be
vocal to get the human's attention to open the door? Seems incredible.
And how does the cat always come home at the same time of 7pm? I
assume its when she gets thirsty but I'm wondering if they have a
biological clock and can estimate time or use the position of the sun.