That's really interesting! It's like the professor is taking payday time loans.
I don't agree with the conclusions, though, such as giving poor people a grace period to pay a bill before slapping a fee on them. Why wouldn't they just put it off until the day they know they get hit with the fee? If you tried to fix this by making the fee occur by random chance, that would be even worse because people overestimate their performance at games of chance.
At the individual level the implications are clear: never let yourself feel low on money or on time. As a society the best prescription is education, for both time and money management.