Well, googling seems to show that the site is legit..
If it is a legit site i think that they are just putting a release date and dont really have a date, just a guess. And as soon as that release date is announced that 181 days will change to whatever the actual date is.
The release date is probably true because look at the publisher company: It says Vivendi, Vivendi owns blizz, and vivendi is based in Europe. So probably vivendi already made it possible to make pre-orders. So basically blizz just makes the game, and vivendi decides when and where to start releasing it.