Yeah, I see now. Unfortunately these people exploited the way I used to make their life easier. :) Well, that's what people usually do.

I updated the kata to retain this easiness but making exploiting harder. :)

The cheating solutions are now marked invalid, of course.

Thanks for noticing!

No, I have not. What's the point?

Everything is not hard after you do it P:

It is difficult not for implementing, but for understanding due to blurred definitions. The exact sequence of actions is not clear. I was able to solve the problem only when rephrase "the end of the even month" to "beginning of odd month".