Friday the 13th, which was the first in October since 2006 according to the Chicago Tribune, might be a day when you’re more wary of black cats crossing your path or walking under a ladder.

You might not know how the superstition came about. Many different theories have been thought of over the years.

Time.com explains that many historians believe the superstition dates back to the Last Supper. That was when Jesus and his 12 disciples, for a total of 13 guests, celebrated Passover together, only to have Judas betray Jesus, who was then crucified the day after on a Friday.

Another story the superstition could have arisen from is when the Knights Templar, “a monastic military order,” were arrested on Friday the 13th in 1307, according to History.com. It was in October, which makes it exactly 710 years ago.

What makes Friday the 13th so spooky is the number 13 itself. History.com also provides some insight on how 13 came to be unlucky, saying that the number 12 symbolizes completeness.

Whether with 12 months in a year or 12 disciples in the Bible, 13 following the complete number 12 could have made people feel uneasy and sparked the superstition of 13 being unlucky.

References in literature and pop culture about Friday the 13th causing bad luck have helped keep this superstition alive in the modern world.

But whether you believe Friday the 13th brings bad luck or not, for some Derby students, the fact that it was a half day of school might have broken that belief.