Standing orders should react to the day that they are scheduled. I can only speak for the UK, but other countries could be the same: banks do not process any standing orders on a weekend or special day/bank holiday. As a result these are queued until the next normal/work day. For salary, the opposite occurs, all payments will be paid before, on the last normal day.
I'd like the options to select whether standing orders are processed, before, after or on these days. That way everyone is catered for.