How to resolve "Call to undefined function" after upgrade to 4.7.27 CRM_Core_SelectValues::datePluginToPHPFormats()
After searching on Jira for the funciton, nothing came up, so searched the codebase from our backup and found the function was in the file: civicrm/civicrm/CRM/Utils/Date.php:1788

It's now gone, along with a lot of other ones!

So I've added the array of date formats to the code to workaround the issue.

//$actualPHPFormats = CRM_Core_SelectValues::datePluginToPHPFormats();
  $actualPHPFormats = array(
    "mm/dd/yy" =&gt; 'm/d/Y',
    "dd/mm/yy" =&gt; 'd/m/Y',
    "yy-mm-dd" =&gt; 'Y-m-d',
    "dd-mm-yy" =&gt; 'd-m-Y',
    "dd.mm.yy" =&gt; 'd.m.Y',
    "M d" =&gt; 'M j',
    "M d, yy" =&gt; 'M j, Y',
    "d M yy" =&gt; 'j M Y',
    "MM d, yy" =&gt; 'F j, Y',
    "d MM yy" =&gt; 'j F Y',
    "DD, d MM yy" =&gt; 'l, j F Y',
    "mm/dd" =&gt; 'm/d',
    "dd-mm" =&gt; 'd-m',
    "yy-mm" =&gt; 'Y-m',
    "M yy" =&gt; 'M Y',
    "M Y" =&gt; 'M Y',
    "yy" =&gt; 'Y',
  );