There are many different theories as to why the number 13 is considered unlucky. One is there were 12 apostles. Judas Iscariot was number 13 and if you are a Catholic you know that he betrayed Jesus,hence the phrase being a Judas. Anyway there are other reasons too.
If you look back in history there were many negative events that happened on this day .There are some people who are so afraid of the day that they actually will not even leave their homes.Psychiatrists have labeled the condition paraskavedekatriaphobia .
Furthermore, hundreds of Knights Templar were arrested on Friday the 13th and Eve was supposed to have bitten the apple on that day.
Most buildings do not have a 13th floor and last but not least let's not forget the number 13 is the number of witches you need for a coven(It Is? ) lol Anyway whichever way you look at it the number 13 absolutely gets a bad rap. As an Italian American I was always told that the number is lucky for Italians.
So while you are out venturing through the day tomorrow(if you're brave enough) be sure to say hello to every Giovanna , Maximo and Luigi you meet ! lol Peace and Namaste