Didn't mean to be rude earlier, guys, but what I did is good: Every year divisible by 4 is a leap year. But every year divisible by 100 is NOT a leap year Unless the year is also divisible by 400, then it is still a leap year. The year that is divisible by 100 is not leap year UNLESS it is divisible by 400! See there? That's exactly what I did. See the if loop: Posted on 09-28-06 6:38 PM Reply | Notify Admin ny serious Java people in here? For some reasons, the following code doesn't work for leap year. Any help/suggestion is appreciated. The classes are Date and TestDate: public void addMonth(int m) { month = month + m; if (month>12) { month-=12; addYear(1); } } public boolean isLeap(int y) { if (y%100==0) { if (y%400==0) return true; -----------> means, if it is divisible by 100 AND 400, return true else return false; ------>if it is divisible ONLY by 100....return false.. } else if (y%4==0) return true; return false; }