I agree that this is a problem. I did the problem in C#. I am fairly confident my original solution was correct, but it was failing a test. After seeing this comment I 'fixed' my solution by subtracting a year from my loop and it works. The issue is with the Random Test, unfortunately without knowing what values are used it is impossible for me to show you mathematically what is wrong with the test. However, if you have a look at the solution I have submitted, you can see how I am looping for 1 less year than I should be.

I am not sure that I understand your problem. Could you give some examples if you want I can examine it. You can see that lots of guys passed the kata; the tests are the same in all languages.