This question is an exact duplicate of:

Applying the date_iso8601 Drupal function in a simple process_callbacks on the public_fields in the class file for each date field works to convert the output/display of the date format, but does not allow that format to be used for filtering by the date value.

  'process_callbacks' => array(

So we need to figure out how to make the query filter use the ISO 8601 date format and support things like partial matches using just YYYY-MM-DD and ensure different operators work as well (>, <, >=, <=).

marked as duplicate by Pierre.Vriens, Community Apr 21 '16 at 12:34

This question was marked as an exact duplicate of an existing question.

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