today = new Date();
day = today.getDay();
month = today.getMonth();

nextImage = new Array(
"images/January.jpg",
"images/February.jpg",
"images/March.jpg",
"images/April.jpg",
"images/May.jpg",
"images/June.jpg",
"images/July.jpg",
"images/August.jpg",
"images/September.jpg",
"images/October.jpg",
"images/November.jpg",
"images/December.jpg",
"images/out.jpg"
);

function chgImg(ImgNum) {
 document.slideshow.src = nextImage[ImgNum];

 if (ImgNum > month)
  {
    document.slideshow.src = nextImage[12];
  }
}