Does the Twelfth Night fall on January 5 or 6? And why is it called the Thirteenth Night (Trettondagsafton) in Sweden? The traditional answer is that it falls on the 5th and here is why?
Here you can see why the Twelfth Day is not among the so called Twelve Days of Christmas.
Having spent some time during the holidays discussing this on Facebook I felt the need to clarify this.
The discrepancy between the English and Swedish way of naming the days after Christmas can easily lead to so called fence post errors, a common issue in computer programming.