MySQL error in file: /engine/modules/calendar.php at line 213

Error Number: 1055

The Error returned was:
Expression #1 of ORDER BY clause is not in GROUP BY clause and contains nonaggregated column 'unfir.dle_post.date' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

SQL query:

SELECT DATE_FORMAT(date,'%b %Y') AS m_date, COUNT(id) AS cnt FROM dle_post WHERE approve=1 AND date < '2020-05-26 21:07:21' GROUP BY m_date ORDER BY date desc