Yeah, I miscounted.
And yes, real time would have been easier. They probably consider the current system a mistake now as well, but changing it would cause more chaos. The only ways to fix it would be either a timeskip; which would stop WoW from being a continuous story. Or a correction of all the dates since vanilla; which would create confusion.
That means its easiest to stick to their current method. So they're highly likely to continue doing so.