As far as I know. "If you use Apple Card to make purchases this month, your first payment will be due September 30." And my signup date was the 10th of August.
Do payments “post” even on a weekend if it is the last day of the month? In other words, for example the last day of August is 31st and a Saturday. If people owe, should they be sure to submit payment within the app on Friday the 30th?
In my experience, as long as you submit payment by the due date, it doesn’t matter if it’s on a weekend or not. They’ll take the money the next business day.