day that is needed, often because large corporate end-to-end systems take longer than the few hours between COB and midnight to complete and have to pass files down a production line of systems. It is also a usual requirement that occasionally some transactions dated on a Friday may be processed on a Sunday or even later. Public holidays, not just weekends, often have to be taken into account. Some systems perform empty runs on the day after public holidays to overcome this problem, but that can't work for every situation and (for e.g. credit card, ATM and GSM billing systems) the algorithm often has to be able to handle DST changes without double-entering transactions.