title: Calculating days difference in a calculated field
body: <p>I have tried every variation I can think of.</p>
  
  <p>I have a table that displays [Appt Date] in a field. I want to subtract that date from today to give me the [Days to Appt].</p>
  
  <p>I have tried several variations in the expression builder of the calculated field</p>
  
  <pre><code>=DateDiff("d",[Appt Date]-Date())
  =[Appt Date]-Date()
  </code></pre>
  
  <p>And so on.</p>
  
  <p>The error message I am continuously presented with is </p>
  
  <blockquote>
    <p>The Expression [APPT Date]-Date() cannot be used in a calculated column.</p>
  </blockquote>
  
  <p>I have tried this in a <strong>Date/Time</strong> calculated field and a <strong>Number</strong> Calculated Field</p>
  
  <p>Your help will be gratefully appreciated</p>