title: Rails and date: get profiles with related ages
body: <p>Hy,</p>
  
  <p>I have a profile x, that has a born_date and then i want to get all the profiles that has more or less 5 years.</p>
  
  <p>If profile x has 20 years, i want every profile that has between 15 and 25 years.</p>
  
  <p>Here i need some date calculations and i dont really know how to do it. You have some ideas? ;)</p>