How long does it take to get used to a hard saddle?
Take it back and get a different one. A decent bike shop will let you do this. I went through 3 saddles the last time.

The goal is that the "saddle fits you", and not, "you fit the saddle". 


  It really doesn't take weeks. 


to determine whether a saddle is right or not! A long ride will do.

An anecdotal note... My current road bike saddle would qualify as a "hard leather saddle". At the time I bought the bike, I didn't like the original saddle, then tried a Specialized, then a Fizik, and then settled on a Selle Italia. I'm not knocking either Specialized or Fizik or any other brand; it's just that the Selle Italia saddle worked for my anatomy, and I often spend an entire day+ sitting on that saddle. Saddles are like shoes, they have to fit the wearer. A 30 mile ride told me which saddle to get.