monthNames = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];

function yearTrans(year) {

  if (year < 1900) {
    year += 1900;
  }
  return year;
} 

function modDate() {

  mod = new Date(document.lastModified);
  document.write( mod.getDate() + " " + monthNames[mod.getMonth()] + " " + yearTrans(mod.getYear()));
}