|This is a new age for an old calendar system
Perhaps you've noticed that your monthly calendar begins with the day of Sunday. I was brought up with the understanding that God created the world in seven days and the last day, the 7th day, happened to be Sunday. For a calendar system like the one we use regularly to hang on the wall to begin on a Sunday, it makes me wonder just how religious people in this country really are, for a yearly calendar that displays each month in a way that suggests Sunday is the first day of the week means that Saturday is the day that ends up being the "7th day". And you know what that means, don't you? It means that every time the first week of the month starts on a Sunday, the seventh day is a Saturday, and, therefore, that month in particular will contain a Friday the 13th.