* @throws NegativeTimeException startDate > endDate
*/
private String generateSecondDuration(Date startDate, Date endDate)
throws NegativeTimeException {
if (endDate.getTime() - startDate.getTime() < 0)
throw new NegativeTimeException("Cannot generate second duration " +
"between (" + startDate + ", " + endDate + ")");
long millis = endDate.getTime() - startDate.getTime();
return (millis / 1000) + " S";
}