"In Ferris Bueller's Day Off, Ferris is living a Groundhog Day situation"

R/Fan Theories:

This theory also justifies his mostly live-in-the-moment, no care for consequences attitude. His fixation on getting married to Sloan is another sign of this - he's desperate for this romance (by all accounts in its early days since the administrator isn't sure who Sloan is dating) to have some kind of meaning because in his head, he's been in a relationship with Sloan for years.

Thirdly, the constant fourth-wall breaking. This is a sign of the strain this time-loop has left on his brain - it has deluded him into thinking he has a constant audience that he can explain all his thoughts to. The camera is essentially his imaginary friend, a result of the trauma of reliving the same day constantly.

The theory is even supported by some of the dialogue - the moment where he looks into the camera and says 'this is the bit where Cameron goes berserk' suggests that he is recalling current events as a memory. Best of all, at the end of the movie when his parents come home and he's in bed, they ask him how he ended up so perfect. His response?

"Years of practice."

...

The theory makes even more sense when you consider that perhaps, like the actual Groundhog Day, the "point" of the loop is to make Ferris reconsider every aspect of his day and approach to life and actually achieve something by helping someone else (Cameron) and perfecting the romance in his life (Sloane)