The longest chess game in history

The one between Ivan Nikolic and Goran Arsovic, played in 1989 in Belgrade. Within more than twenty hours, 269 moves were played in a game over draw. FIDE had, at that time, changed the rule of 50 moves (if the two players do not catch a piece or move a pawn within 50 strokes, the game ends in a tie) extending it to 100. After that episode, we went back at 50.