If you have Friggatriskaidekaphobia, you and 17 to 21 million other people may have an anxious day today. Today is Friday the 13th. Friggatriskaidekaphobia is the fear of Friday the 13th! While there is no causal evidence that links Friday the 13th to any bad event, this day can actually paralyze people with fear. We joke about the day, but it is no joke to those filled with anxiety.