title: Convert string to date format in azure data factory using set variable
body: <p>I have string date in set variable &quot;20211222&quot;
  And I want to convert it into date like 2021-12-22.
  And I have use this function in variable set dynamic content</p>
  <p>@formatDateTime('20211222', 'yyyy-MM-dd')</p>
  <p>But error occur <strong>In function 'formatDateTime', the value provided for date time string '20211222' was not valid. The datetime string must match ISO 8601 format</strong></p>
  <p>Is there any other function to convert this string &quot;20211222&quot; into date?</p>