high school, meaning of dreams

ill just make it short.. the scenario is im still in high school and in the current year and in my dream im with my hs friends and 1 of them already past away not really sure when, but in my dream he's there with us, then i ask him. "hey, your already dead right? " and then he laugh " and i ask him again. " if ur not dead.. what year is it? he then replied 2010, then all of us laugh and i answered "wrong! its just 2009" and then said, "didnt u know all of us though that u are dead already?" then i look at other way and thinking i know he's dead.. then the scenario change..(that what always happen in a dream) my question is.. whats about the year.. why did he answer 2010, whats with the year 2010 and why did i dream of a friend that we're not that close and the last time i saw him is 1996.. that was 13yrs ago. hope u can answer the meaning of dreams