Jesus died on a Friday and Judas was the 13th disciple... or so they say.
Actually, Jesus most probably died on a Wednesday. Too long to explain, but Googling will give plenty of information about that.
Also, Judas Iscariot was one of the original 12 disciples, not the 13th - unless you count Jesus as the 1st. After Judas committed suicide, another was chosen to fill the dozen. Was he Matthias who was selected by the disciples (acts 1:26), or Paul, whom Christ selected?
Friday the 13th is a widespread jinx, at least it's known in the Western world. An interesting fact is, that the 13th day is a Friday more often than any other day.