National Accident Day (or Accident Day, kansallinen tapaturmapäivä) is a day to raise awareness about automotive safety in the country of Finland.[1][2] It is chosen to be on Friday the 13th each year and because there is at least one Friday the 13th per year on the modern Gregorian calendar, this is always possible.[2]

https://en.wikipedia.org/wiki/National_Accident_Day_(Finland)#cite_note-Fri13-2

A bit of bad news for all of you who suffer from friggatriskaidekaphobia—all years will have at least one Friday the 13th. The good news is that there cannot be more than three Friday the 13ths in any given calendar year. The longest one can go without seeing a Friday the 13th is 14 months.

https://www.timeanddate.com/calendar/13-things-friday-13.html

Nadal nie jestem przekonany, że zawsze musi być.

#matematyka #kalendarz