http://en.wikipedia.org/wiki/Friday_the_13th
"Phobia
The fear of Friday the 13th is called friggatriskaidekaphobia (Frigga being the name of the Norse goddess for whom "Friday" is named and triskaidekaphobia meaning fear of the number thirteen), or paraskevidekatriaphobia[1][2] a concatenation of the Greek words Paraskeví (?????????, meaning "Friday"), and dekatreís (?????????, meaning "thirteen") attached to phobía (?????, from phóbos, ?????, meaning "fear"). The latter word was derived in 1911[citation needed] and first appeared in a mainstream source in 1953.[3]"
"Tuesday the 13th
In Spanish-speaking countries, instead of Friday, Tuesday the 13th (martes trece) is considered a day of bad luck.[11] 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."