Researched and written by Mike Smith – February 2026
When the calendar lands on Friday the 13th, much of the English speaking world glances sideways at ladders, black cats, and travel plans. In Spain, however, the date passes with little more than a shrug. The real eyebrow raiser arrives when the 13th falls on a Tuesday.
In Spain, the traditional unlucky day is martes trece, Tuesday the 13th. The roots lie in language and mythology. Tuesday is named after Mars, the Roman god of war, whose portfolio included bloodshed, conflict, and general planetary turbulence. Pair that with the number 13, long considered ominous in Western tradition, and you have a date wrapped in symbolic storm clouds. A well known Spanish proverb captures it neatly: “En martes, ni te cases ni te embarques,” advising people not to marry or set sail on that day. The superstition has deep cultural roots and is also shared in parts of Greece and Latin America.
So why does the United Kingdom and many other countries single out Friday the 13th instead?
In countries such as the United Kingdom, the United States, Ireland, Canada, Australia, and New Zealand, the anxiety gathers around Friday rather than Tuesday. The explanation blends religious tradition and folklore. In Christian belief, Friday is associated with the crucifixion of Jesus, which gave the day a somber undertone in medieval Europe. Meanwhile, the number 13 developed its own uneasy reputation, often linked to the Last Supper, where 13 people sat at the table before betrayal and death followed.
Over centuries, these two strands braided together into a single superstition. By the early twentieth century, popular culture amplified it. The 1907 novel ‘Friday, the Thirteenth’ by Thomas W. Lawson helped circulate the idea in the English speaking world, and the 1980 horror film ‘Friday the 13th’ cemented it in modern imagination, complete with cinematic terror and a franchise to match.
In short, Spain did not opt out of superstition. It simply assigned its bad luck to a different square on the calendar. Depending on where you stand, the 13th may carry a shadow, but the weekday that casts it changes with culture.
