Your code/serial number looks like a JS-Style Timestamp to me, which would be milliseconds after 1.1.1970. You could use a function like this to convert it into a date:
dateAddMinutes(convertToDate("1.1.1970"), tbDateCode / 60000)
I used a form with a calculated value control with the above formula, and a TextBox named "tbDateCode" where you can enter the code (e.g.1385528400000, which would be November 27, 2013).
You should then be able to compare this to any other date value using just the lessThan or greaterThan functions.
Hope this helps