{ f (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; } --well , as per my reading, you should have following conditions 1) the year is divisible by 4 (NOT the sufficient condition, so you have to look into) (a) is the year divisible by 4 and not by 100? if yes, it's a leap year else not (b) is the year divisible by 4 and by 100? (NOT the sufficient condition, so you have to look into) (i)is the year also divisible by 400 as well? if yes, it's a leap year, else not obviously, it's not a leap yr if its not divisible by 4. sajhauser is right and she provided the link as well. you should have gone through it :P LooTe