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Friday the 13th: Why We Fear It; Why It Can't Strike Again in 2012
Today is third Friday the 13th of the year—the maximum possible.
Triskaidekaphobia sufferers, your nightmare is nearly over. Though today is the third Friday the 13th of 2012, another is impossible, at least as long as we mark time with the Gregorian calendar.
"You can't have any [years] with none, and you can't have any with four, because of our funny calendar," mathemetician Underwood Dudley said.
In many ways the Gregorian calendar, which Pope Gregory XIII ordered the Catholic Church to adopt in 1582, works just like its predecessor, the Julian calendar—with a leap year every four years.
But the Gregorian calendar skips leap year on century years except those divisible by 400. For example, there was no leap year in 1900, but there was one in 2000. This trick keeps the calendar in tune with the seasons.
Friday the 13th: Why We Fear It; Why It Can't Strike Again in 2012
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