title: convert date yyyymmdd to yyJJJ or Julian Date
body: <p>Need a formula in excel and c# to convert data in "yyyymmdd" format to julian date format "yyJJJ"?  Where "JJJ" is the Julian date of day submitted.  Is JJJ a number from 1 to 365 or 999 or 366?  I don't think its 366, but we do have leap year so it could be leap year. </p>
  
  <p>In Excel I'm trying to use the following:</p>
  
  <pre><code> =Year() &amp; DAYS360("20110101","20110930")
  </code></pre>
  
  <p>In C# I'm using now() to get the current date.   But I'm want the number of days between Jan 1st, and current date.  Not sure if this is the correct prototype formula: </p>
  
  <pre><code>Prepend Two digit year format to the following
      Number of Days between "20110101" and "20110930" in "YY" format 
  </code></pre>