seems been sometime away from Java: calendar date difference

I was using this

if( (new Date().getTime() - tradeDate.getTime()) > 1000 * 60 *60 * 24 * 30){
..
}

for making sure trade date not older than 3 months, which then exactly encountered the round off problem mentioned here,
http://tripoverit.blogspot.com/2007/07/java-calculate-difference-between-two.html.

should instead using calendar.before()

    java.util.Date tradeDate = ct.getActionDate();
	Date now = new Date();
	Calendar threeMonBef = Calendar.getInstance();threeMonBef.setTime(now);
	threeMonBef.add(Calendar.MONTH, -3);
	
	Calendar cal1 = Calendar.getInstance();cal1.setTime(tradeDate);

if( cal1.before(threeMonBef)){
..
}

==================================================updated Aug 15, 2012
//only date information should be maintained, instead of datetime, to avoid problem due to timezone difference.

    /**
     * Get previous Business Day of the current system date.
     * Note that this method is heavy because it calls isBusinessDay, which required Database query, multiple time.
     * So, this should be called when it is really required.
     * @param channelCtx
     * @return
     */
    private Date getPreviousBusDay(ChannelContext channelCtx) {


        // yes. I believe that GOCM v1 works only for Tokyo.
        Calendar nowInTokyo = Calendar.getInstance(TimeZone.getTimeZone("Asia/Tokyo"));
        // for testing the situation that Date part is different between Tokyo and GMT.
//        nowInTokyo.set(Calendar.AM_PM, Calendar.AM);
//        nowInTokyo.set(Calendar.HOUR, 7);
//        nowInTokyo.set(Calendar.MINUTE, 30);

        // copy the tokyo date to GMT/PDT calender. truncate datetime part.
        // This is required to get correct result from isBusinessDay method when prev calender date is Holiday.
//        Calendar prevBusDay = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
        // weblogic server in US/ewd uses PDT , local dev may use different
        Calendar prevBusDay = Calendar.getInstance(); //use the timeZone of the host
        prevBusDay.set(Calendar.DATE, nowInTokyo.get(Calendar.DATE));
        prevBusDay.set(Calendar.AM_PM, Calendar.AM);
        prevBusDay.set(Calendar.HOUR, 0);
        prevBusDay.set(Calendar.MINUTE, 0);
        prevBusDay.set(Calendar.SECOND, 0);
        prevBusDay.set(Calendar.MILLISECOND, 0);

        prevBusDay.add(Calendar.DATE, -1);
        while(!isBusinessDay(prevBusDay.getTime(), channelCtx)){
            prevBusDay.add(Calendar.DATE, -1);
        }
        return prevBusDay.getTime();
    }