Meta Query Compare with Date

It looks like it is the date format. I tried it with the format 2020/10/10 (YYYY/MM/DD) and it worked as expected. You can also use hyphens as delimiters (YYYY-MM-DD), or omit them entirely. Since you’ve already formatted the date, you don’t need to use the date() function.

$metas[] = array(
'key' => 'event_date',
'value' => array('2020/10/10', '2020/10/11'),
'compare' => 'BETWEEN',
'type' => 'DATE' );