The Japanese say the Pearl Harbor attack took place on Dec 8, 1941
Because Japan is on the other side of the International Date Line, that's when it happened, Japanese time. However, the attack took place in Hawaii on our time.
Likewise, the Explorer I launch took place from Florida on Jan 31st. Are we to base every historical event on the time zone of the observer or where the event took place? It'd probably be a lot simplier to use the date where the event took place.