Expiry Date

var curDoc = app.doc;
var date1 = curDoc.getField("DateField");
var date1Value = date1.value;
var actualDate1 = new Date(date1Value);
var curDate = new Date();
// some useful information:
console.show();
console.clear();
console.println("Inputted date: " + date1Value);
console.println("Actual date object: " + actualDate1);
console.println("Current date object: " + curDate);
console.println("Test result: " + String(actualDate1 > curDate));
console.println( "Actual date full year: " + actualDate1.getFullYear());
console.println("Current date full year: " + curDate.getFullYear());
console.println("Inputted date 2 digit year: " + actualDate1.getYear());
console.println("Current date 2 digit year: " + curDate.getYear());
// end of some useful information;
if(actualDate1 > curDate) {
console.println("yeah");
}
else {
console.println("boo");
}

Use Date.getFullYear() instead of getYear(): Date.prototype.getFullYear() - JavaScript | MDN

This will get rid of the 2 digit year problem you are seeing ("118"). The reference to DifferentField is very likely in a different script. Check all your scripts to see which one is using the name of an invalid field.

It's not a good idea to reference the field your validation script belongs to via the getField() method. All the information you need is available via the event data structure - e.g. event.value as the entered value.

app.doc is not documented. Use 'this' instead to get a reference to the current document - but in this case, because we can use event, that's not even necessary.

You may have to use the until.scand() method to parse your date string of mm-dd-yyyy

The following should work:

var date1Value = event.value;
var actualDate1 = util.scand("mm-dd-yyyy", date1Value);
var curDate = new Date();
// some useful information:
console.show();
console.clear();
console.println("Inputted date: " + date1Value);
console.println("Actual date object: " + actualDate1);
console.println("Current date object: " + curDate);
console.println("Test result: " + String(actualDate1 > curDate));
console.println( "Actual date full year: " + actualDate1.getFullYear());
console.println("Current date full year: " + curDate.getFullYear());
console.println("Inputted date 2 digit year: " + String(actualDate1.getFullYear()).substring(2,4));
console.println("Current date 2 digit year: " + String(curDate.getFullYear()).substring(2,4));
// end of some useful information;
if(actualDate1 > curDate) {
     console.println("yeah");
}
else {
     console.println("boo");
}