title: Calculating holiday dates
body: <p>I have to create "holiday" table and then create php script so I could show it on my site.</p>
  
  <p>Holidays can be specific, like 15.05.2012 - 15-th of the may.</p>
  
  <p>And non-specific: First(or second, third) sunday of july</p>
  
  <p>Is there any way to create calculated column, so this phrase "First(or second, third) sunday of july", could turn into x.07.2012. </p>