This question came about because of my last question, but I felt this deserved it's own discussion.
This wiki answer on the List of all badges with full descriptions post regarding the yearling badge does not seem right to me. I already made one minor edit as a result of the last discussion. But I don't feel qualified to make additional edits.
The part I take exception to is this:
If the number of years is not an even number (1 or 2). For example, if at the 2 year mark you don't have the 400 required reputation, the number of years still continues to increase. So half way through year 2, you'd need 2.5 × 200 reputation, or 500 reputation, to qualify for the second year badge.
Here's how I read that. If a user gains rep that pushes him over the 400 mark at 2 years and 11 months, he would not qualify for yearling because he now needs 584 rep to qualify, e.g. (2 + 11/12) * 200.
But I was browsing the yearling page trying to understand the calculation. And here is a user active for 2 years and 11 months with rep of 408 being awarded his second yearling. And that is just one example. So that seems to contradict the description in the wiki answer.
Perhaps someone better qualified than me can improve that answer. Maybe the whole bullet point just needs to be removed altogether. Even it was true at one time, it does not appear to be true any longer. Perhaps info from Sha Wiz Dow Ard's answer can be incorporated.