In Spain there is a proverb which goes: “En martes, ni te cases ni te embarques.” (On Tuesdays, neither get married nor embark on a journey.) According to wikipedia: “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) an unlucky day.”
Most likely the origin of this superstition about Tuesdays being unlucky has to do with Hellenistic astrology. The Babylonians had assigned each of the visible wandering stars (‘planets’) to a day of the week. Sun got Sun-day; Moon, Monday; Mars, Tuesday; Mercury, Wednesday; Jupiter, Thursday; Venus, Friday; and Saturn, Saturday. The English names for the days preserved the planetary rulers but alluded to the names of Norse gods instead of Greek or Roman gods.
The texts of Hellenistic Greece and the Persian-Arabic astrologers made their way into Europe through Spain, where they were translated into Latin. Images such as the following of the planets ruling each day and hour of the week were familiar to the educated classes of Europe during the Renaissance:
The week begins with the Sun ruling the first hour of daylight on Sunday. In the above diagram you can see that Mars rules the first hour of daylight on Tuesday, the 3rd day of the week. At nightfall (sunset) on Tuesday, Saturn takes over as the first ruler of Tuesday night. The first planet to rule the day, or the night, hours has a special influence over the periods of daylight and nighttime, respectively.
In ancient astrology Mars and Saturn were the two principal malefic planets, causing harm and being inimical to life. Mars was especially dangerous during the daylight hours because the heat of the Sun enhanced the natural fiery nature of Mars, making him more impulsive, aggressive and violent. Saturn was especially harmful during nighttime hours because the coldness of the night enhanced Saturn’s natural tendency to limit, constrict, and chill the life out of living creatives. Perhaps Robert Frost had Mars and Saturn in mind when he wrote his poem “Fire and Ice” which debates whether the world will end in fire or in ice.
The astrological teachings about planetary days and hours and the nature of malefic planets being enhanced by the “sect” (diurnal or nocturnal nature) of the chart apparently got codified in the the Spanish proverb: “En martes, ni te cases ni te embarques.”