I still love the fact that if you only implemented the first rule or had the knowledge to implement all 3 rules, it would totally work, but if you implemented 2 of the 3 rules you were wrong.

It taught me a great lesson about results not proving correctness as how you got there could bite you later.

I don't get why people don't know all three rules. In elementary school when the calendar is taught, the complete rules of the leap year were simply taught by the teacher. We even joked about people born on the 29th of February. Why wasn't this taught everywhere?

Heh, this sentence seems particularly relevant to this whole discussion...

> This method works fine for the year 2000 (because it is a leap year), and will not become a problem until 2100, when older legacy programs will likely have long since been replaced.