public long getFirstMillisecond(Calendar calendar) {
        int year = this.serialDate.getYYYY();
        int month = this.serialDate.getMonth();
        int day = this.serialDate.getDayOfMonth();
        calendar.clear();
        calendar.set(year, month - 1, day, 0, 0, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        //return calendar.getTimeInMillis();  // this won't work for JDK 1.3
        return calendar.getTime().getTime();