From 27 May, New Zealand banking providers switch to 7-day payment processing. This means that direct debit payments can be processed on any day of the week, including weekends.
So if your monthly direct debit payment, on the 20th of the month, is during the weekend, or your weekly or fortnightly direct debit is due on a public holiday, for Tuesday and Thursday payment days, your payment will be processed on this day and not the next business day.
This is just a transactional change all New Zealand banks are making, so all you have to do is ensure that you have enough funds in your bank account on your usual payment date.