Birds of a feather flock together

When an unlucky number coincides with a "black day"

It's just as well there's no thirteenth month. Imagine what could go wrong on Friday 13/13! Twice as much bad luck. The concept of a 13th month is not as far-fetched as it seems. Before the advent of solar time, people lived according to the lunar calendar. So because a year has 13 full moons (each lunar cycle being around 28 days), there were 13 months. When the solar calendar was introduced, every effort was made to stop people using the lunar one – which led to the number 13 acquiring negative connotations. The phenomenon gathered momentum over the centuries: the day has two times twelve hours, the year twelve months, and Jesus had twelve apostles. The 13th to arrive was Judas, the betrayer. In the fairy tale, Sleeping Beauty, there were only 12 golden plates, as a result of which the 13th fairy, who had to be left out of the feast, placed a curse on the princess. For a long time, 13 was commonly referred to in German-speaking regions as the "devil's dozen". Similarly, Friday is seen by some as having negative associations – a "black day": it's the day that Jesus died and Adam and Eve were banished from the Garden of Eden. In 1929 "Black Friday" signalled the Wall Street crash and the start of the Great Depression. At the time, unlucky number 13 and Friday with its negative associations were still separate concepts. Why and how they came together isn't known for sure. Birds of a feather flock together, they say. It's human nature to want to augment and intensify, so one thing led to another. Just make sure no black cat crosses your path that particular day!