title: excel conditional formatting validate date
body: <p>I try to evaluate if a cell contains a valid date. If the content is not a valid date, the cell should be colored red. I want to do this without vb. On SO i got told, this is possible using only conditional formatting</p>
  
  <p>Here is my try:</p>
  
  <p><a href="https://i.stack.imgur.com/k2gBQ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/k2gBQ.png" alt="wer das liest ist doof"></a></p>
  
  <p>This doesn't work. I think the formular is fine, because i get no error message, but still no success.</p>
  
  <hr>
  
  <p>Another try was to use Highlight Cells Rules and depending on a date occurring.</p>
  
  <p><a href="https://i.stack.imgur.com/wtfBX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wtfBX.png" alt="hoch vom turm, kackt der wurm"></a></p>
  
  <p>But here i can only use specific rules, like date is from this week, or this month, or past week. I can not say is a valid date or is a date between X and Y.</p>
  
  <p><a href="https://i.stack.imgur.com/fOvXX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fOvXX.png" alt="enter image description here"></a></p>
  
  <p>Any ideas how i can achieve my goal to set background-color of cells with invalid date-formats?</p>