title: IQueryable Lambda Expression for every Nth date
body: <p>I have a calendar table that contains a series of dates, and I'm trying to write a query that gives me every N dates.  I can do this in SQL without difficulty, but when writing it in a <code>IQueryable</code> with a <code>Where</code> condition, I can't seem to get it to work.</p>
  <p>As an example, I can do something similar to this in SQL to get every third date:</p>
  <pre><code>Select _date 
  from Calendar 
  where datediff(day, startdate, _date) % 3 = 0
  </code></pre>
  <p>but a similar <code>IQueryable</code> lambda expression throws a <code>System.ArgumentException</code> (when the query is executed)</p>
  <pre><code>var q = dbcontext.Calendar
                   .Where( c =&gt; (c._date - startdate).Days % 3 == 0);
  </code></pre>
  <p>Is there some other way this could be written to make it work?</p>