\Cake\I18n\Time::setToStringFormat('Y-m-d H:i:s');
\Cake\I18n\Date::setToStringFormat('Y-m-d');
\Cake\I18n\FrozenTime::setToStringFormat('Y-m-d H:i:s');
\Cake\I18n\FrozenDate::setToStringFormat('Y-m-d');
this maybe help
\Cake\I18n\Time::setToStringFormat('Y-m-d H:i:s');
\Cake\I18n\Date::setToStringFormat('Y-m-d');
\Cake\I18n\FrozenTime::setToStringFormat('Y-m-d H:i:s');
\Cake\I18n\FrozenDate::setToStringFormat('Y-m-d');
this maybe help