In Spanish-speaking countries, instead of Friday, Tuesday the 13th (martes trece) is considered a day of bad luck.
The Greeks also consider Tuesday (and especially the 13th) to be an unlucky day. Tuesday is considered to be dominated by the influence of Ares (Mars), the god of war. A connection can be seen in the etymology of the name in some European languages (Mardi in French or martes in Spanish). The Fall of Constantinople to the Ottomans happened on Tuesday, May 29, 1453, fact that strengthens the superstition about Tuesday. In addition, in Greek the name of the day is Triti (Τρίτη) meaning literally the third (day of the week), adding weight to the superstition, since bad luck is said to "come in threes".
According to the Stress Management Center and Phobia Institute in Asheville, North Carolina, an estimated 17 to 21 million people in the United States are affected by a fear of this day making it the most feared day and date in history. Some people are so paralyzed by fear that they avoid their normal routines in doing business, taking flights or even getting out of bed. "It's been estimated that [US]$800 or $900 million is lost in business on this day". Despite this, representatives for both Delta Air Lines and Continental Airlines say that their airlines do not suffer from any noticeable drop in travel on those Fridays.
The Dutch Centre for Insurance Statistics (CVS) on June 12, 2008, stated that "fewer accidents and reports of fire and theft occur when the 13th of the month falls on a Friday than on other Fridays, because people are preventatively more careful or just stay home. Statistically speaking, driving is slightly safer on Friday the 13th, at least in the Netherlands; in the last two years, Dutch insurers received reports of an average 7,800 traffic accidents each Friday; but the average figure when the 13th fell on a Friday was just 7,500."