The Sums, 79 or 80?

Just done the sums............ We leave Manchester on 4th Jan 2011 and return on 24th March, which actually equals 79 days.  However, when we fly from Fiji to LA we encounter 2 days in one, as we cross the international date line.  Thus making it exactly 80 days. We leave Fiji having had Sunday lunch and dinner and arrive in LA in time for Sunday lunch .... a nine and a half hour flight later!