Another time question

[Seymore4Head]

I never really cared enough to ask anyone, but something like my cable
bill is 98$ a month.  Do companies (in general) consider a month every
30 days or every time the 14th comes around? 

I did rent a car once during a time change and I only got to keep the
car 23 hours.

As another side note I have had drug prescripts that were 28 days was
considered a month supply.  The would be 4 weeks instead of one month.