title: Google Sheets convert Text String cell into Date + Duration cell
body: <p>I get a csv file which I import into a google sheet.
  I want to calculate the difference between two "Date Time" combination fields, which are now Text fields and not "Date Time" fields.
  Before May they were proper "Date Time" fields in DD.MM.YYYY 00:00, which Google Sheets could work with to calculate the difference in the duration for me. "Updated - Created = Difference". Now it's a text field with the wrong format and the auto convert or manual setting doesn't work. And I work here with a few hundred data sets. So via hand it's a bit rough work...</p>
  
  <p>The DATEVALUE function doesn't work for me. And it was the only related thing I could find.</p>
  
  <pre><code>Created         Updated         Difference
  07/May/18 06:54 07/May/18 07:14 #VALUE!
  07/May/18 07:19 07/May/18 07:28 
  07/May/18 07:02 07/May/18 07:56 
  </code></pre>
  
  <p>Example how it should look like (Slash or Dot shouldn't matter):</p>
  
  <pre><code>Created         Updated         Difference
  07.May.18 06:54 07.May.18 07:14 00:20
  07.May.18 07:19 07.May.18 07:28 00:09
  07.May.18 07:02 07.May.18 07:56 00:54
  </code></pre>
  
  <p>Error code:</p>
  
  <pre><code>Error
  Function MINUS parameter 1 expects number values. But '07/May/18 07:14' is a text and cannot be coerced to a number.
  </code></pre>
  
  <p>Thanks for your help.</p>