Certain dates never leave us- including dates that close loved ones are born and pass on. I have no doubt that Casey knew the exact date that she murdered Caylee and that when confronted by her mother, she threw the June 9th date out there in order to support her "the nanny stole Caylee" lie. If the June 9 date was not dispelled, when Caylee's body was found it would have shown that she died around June 18, therefore "proving" that she died after being kidnapped. Casey wrote her statement referring to June 9, I think she fed this information to her mother- and CA in her highly emotional state at that moment, did not consider when Father's Day was. I don't think Casey counted on video evidence countering her lie.