pereaa yeah same here but in my case the last day of high school was in May(which I put it correctly as the last day I attended high school-5/2008) ,and the day my official high school diploma was signed is in December 2008,but what I put on the application was August 2008.Honestly now that I look at it again I do not understand where that August come from.Only explanation is probably that in my country they issued what is called “Temporary high school diploma” for those who have passed the high school graduation exam earlier than the official diploma because it always took them a while to print out the official form,so I might have put the date of that form in my application.But still that it just a guess and now I do not keep that temporary form anymore so I have no proof of that.