coffee from seeds of dates
Handbook of Indices of Food Quality and Authenticity p474:


  The most important coffe substitute is undoubtedly chicory
  ...
  Chicory itself is reportedly adulterated by roasted beetroot
  ...
  Barley, malt, rye have been used...
  Seeds which have been used include chickpeas, peanuts, soybeans, other beans
  ...
  Date seeds contain less extractives than coffee...


All are roasted somehow. 
Coffee: Related Beverages gives some roasting directions, but I don't immediately see a protocol for date seeds.

Roasted Kentucky Coffee Tree seeds are even still used occasionally.

If I wanted to grind date seeds, I'd smash them with a hammer first. Many seeds are unbelievably tough until broken.