Friday the Thirteenth

To this day Friday the Thirteenth is considered to be a bad day.  People are still cautioned to be careful on Friday the Thirteenth.

Why is Friday the Thirteenth considered to be a bad day?

Ask the Knights Templar.  This was the day that they were arrested in France by an agreement between the Pope of the Catholic Church and the King Philip the Fair of France.  The Knights Templar Arrest is said to have occurred on Friday the Thirteenth on 13 October 1307.  Many of them were then tortured and/or then murdered by the Christians often by Burning at the Stake. 

This could be the reason this date is considered a bad day.