Friday the 13th is the superstition found in English-speaking countries. The relevant phobia is called in English Paraskavedekatriaphobia, from the Greek words "Friday", "thirteen" and "phobia".
This prevention spread to English-speaking countries in the 19th century and spread to the rest of the world through the horror film "Friday the 13th" (1980). Various theories have been expressed about its origin, such as:
On Friday the 13th (October 13, 1307) the Order of the Templars was exterminated by the army of King Philip of France.
It was Friday when Eve gave Adam the forbidden fruit, causing them both to be expelled from Paradise.
The Great Flood of the Bible took place on Friday.
Christ was crucified on Friday.
13 is the most unfortunate number, which breaks the harmony of 12 (12 Gods of Olympus, 12 feats of Hercules, 12 tribes of Israel, 12 disciples of Christ, 12 Imams, etc.). Adding the number "one" forms the beginning of a new cycle. The unknown, represented by the number 13, causes people anxiety and so they began to associate it with unfortunate events.
In computer science there is a virus called "Friday the 13th", which was created in Israel in 1988. It is activated when the computer calendar shows Friday the 13th, resulting in a slowdown in its operation.
The Greeks and the Spanish-speaking peoples, however, have Tuesday 13 as a jinx day. In general, Tuesday is considered an occult day, that is, dangerous and unlucky for these peoples. For the rest of the peoples the jinx day is Friday 13.
The Spanish express the day with the proverb "En martes, ni te cases ni te embarques" ("On Tuesday, do not get married and do not start a journey"). Something similar happens in Greece as the superstitious believe that on Tuesday we should avoid starting any work, attempting a trip or getting engaged. On the contrary, Tuesday is the perfect day for magic.
According to Greek tradition, Tuesday is considered bad day, as on this day Constantinople fell to the Ottoman Turks (Tuesday, May 29, 1453). As the "father" of Greek folklore Nikolaos Politis (1852-1921) observes, this interpretation is coming from the West, since the contemporaries in the West also attributed that national calamity to the destructive influence of the day. Evidence for this prevention has existed since 1164.
According to Nikolaos Politis, the explanation of superstition must be sought in astrological predictions. According to them, the planet Mars is dominant on Tuesday, while at some time of the day (the "bad time") it prevails together with the planet Saturn. That's why this time is so dangerous. But because no one can identify it, the whole of Tuesday is treated as an occult and bad day.
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Tuesday is a lucky day for the Jews, because of the double mention of the word "good" in the Old Testament (Genesis, ch. A, verses 10 and 13)