The extract-by date specified can be any future date. When the user double-clicks the JAR file and it runs, a check is made against the system clock. If the "extract-by" date has past then the expired message is displayed. The text of this message can be altered.
When an extract-by date is used SE-Pro scrambles the data inside the JAR so that simply unzipping the JAR won't get around the fact that the JAR may have expired.