title: Determining durration between dates
body: <p>I'm still pretty new to programming in BASH and i'm racking my brain on a problem. I'm trying to code a script for my work that would make it easy to calculate a refund on a given package cancelled before it's regular end date. Now the simple stuff like inputs and other such things I'm sure I can figure out with googling and experimentation (though should you choose to help with that I would be most appreciative).</p>
  
  <p>What i'm not sure I could find how to do on my own is a script or set of commands that would be able to calculate the number of days / months between two dates and use that variable to calculate the total ammount of refund. I'll try and explain what I am trying to do here:</p>
  
  <p>Input two dates (MM/DD/YYYY format) and get the difference in months and day, IE 3 months 13 days.</p>
  
  <p>Input Base monthly rate</p>
  
  <p>(Base * # of months) + ((base/30) * # of days) = Ammount customer used</p>
  
  <p>Input how much customer payed - Ammount used = Ammount to be refunded</p>
  
  <p>Then preferably it prints it in a manner that one could use to "show their work"</p>
  
  <p>I know this is a bit much to ask for help with but I really could use a hand with the date calculator.</p>
  
  <p>Thanks for any help in advance!</p>
  
  <p>PS I did do a bit of searching beforehand and I found questions SIMILAR to this but nothing that really fit exactly what I needed.</p>