var date = new Date("September 21, 2009");
var description = "our next concert";
var now = new Date();
var diff = date.getTime() - now.getTime();
var days = Math.floor(diff / (1000 * 60 * 60 * 24));

if (days > 1) {
document.write(days+1 + " days until " + description + "!");
}
else if (days == 1) {
document.write("only two days until " + description + "!");
}
else if (days == 0) {
document.write(description + " is tomorrow");
}
else if (days == -1) {
document.write(description + " is today!");
}
else if (days < -1 && days > -5) {
document.write("You have just missed a great concert!");
}
else {
document.write("");

}