I am trying to determine if one date field is greater than the other. I have two date fields - one is a regular date field (date_of_event). The other is a formula date field (valid_event_date) that returns today's date + 14 days. I am validating the first field with this formula but getting an error: Original Formula if ({!date_of_event}
Try
var d1 = new Date("{!date_of_event}");
var t1 = d1.getTime();
Than compare t1 with similar value from other date.
Please check Chapter 6 for examples.