Which day is unlucky?

Today is Tuesday the 13th and for people in Spanish-speaking countries (and also for Greeks and Romanians) it is considered to be an unlucky day. But why Tuesday? In English-, Portuguese-, and French-speaking countries it is Friday the 13th which is seen to bring bad luck.

The common factor here is the number 13, but why is this number feared by some people? It isn't very clear why but many hotels, hospitals, roads, and buildings miss out the number. There is seldom a floor thirteen or a room thirteen. The phobia even has a name: Paraskavedekatriaphobia. Try saying that! Some people say that 13 is an unlucky number because there were 13 people sat at the Last Supper where Jesus Christ and his twelve disciples ate a meal together before Christ was betrayed by Judas Iscariot - an act which led to the crucifixion of Christ.

Friday is considered to be unlucky by some people because it is the day that Christ was crucified, it is the day on which executions were commonly held in the UK and the day that is commonly cited in the Bible as the day on which bad things happened such as the start of the Great Flood, the temptation of Eve and the destruction of the Temple of Solomon.

Another theory to the origins of the Friday the 13th superstition lies with the Knights Templar as suggested in Dan Brown's popular book 'The Da Vinci Code'. On Friday October 13th 1307 the King of France ordered the arrest, trial and subsequent torture of Knight Templars.

The theory behind Tuesday (martes) being an unlucky day is related to Mars, the God of War which implies death and negativity.

All of this makes sense. It only becomes confusing when you realise that the Italians apparently believe that Friday the 17th is in fact the most unlucky of days. I wonder why?