Originally Posted by
koroleon
That's common for flights that cross the date line, e.g. SYD-SFO or AKL-SFO. For these flights, in the opposite direction you arrive two days later than your departure date.
Also common for flights between cities which are close together but have a time zone change between them, for example SBN - ORD and ATL - BHM frequently have arrival times "before" their departure times.