Today is an unlucky day
This may be one of the most widespread superstitions in the United States today. While there's no definitive agreement on its origins, the notion that Friday equals gloom and doom may stem from the belief that Jesus Christ was crucified on this day. In numerology, 12 represents completeness (think lunar calendar, the hours on a clock) so the following numeral has bad associations. Put those two beliefs together and you've got a very ominous day. Of course, the franchise of horror movies by the same name may have amplified the associations with misfortune.