Martes y trece ⇒ Friday 13th (Bad luck day)
“En trece y martes ni te cases ni te embarques.”⇒ On Tuesday 13th neither marry nor board a ship.
“Para un hombre desgraciado, todos los días son martes.”⇒ For an unlucky man, everyday is Tuesday.
“Cada martes tiene su domingo.”⇒ Every Tuesday has its Sunday.
(Exhorts to optimism, reminding that bad comes in alternation with good. In this Spanish proverb “good” is represented by Sunday, a festive day in Christian culture, whereas Tuesday, a week-day of less joyous character, stands for “bad”.)