In adddition to hatsumatsu: Writing the timestamps should probably consider the current timezone settings of your WP installation. I was struggling with that for several hours now, checking the timestamps back and forth. Here’s my approach:
/**
* Convert values of named ACF date time pickers from Y-m-d H:i:s to timestamp
* @param string $value unmodified value
* @param int $post_id post ID
* @param object $field field object
* @return string modified value
*/
function acf_save_as_timestamp( $value, $post_id, $field ) {
if( $value ) {
$tz = new DateTimeZone(get_option('timezone_string'));
$date = DateTime::createFromFormat('Y-m-d H:i:s', $value, $tz);
$value = $date->getTimestamp();
}
return $value;
}
add_filter( 'acf/update_value/name=your_field_name', 'acf_save_as_timestamp', 10, 3 );
Or in case you want all date_time_pickers saving timestamps:
add_filter( 'acf/load_value/type=date_time_picker', 'acf_load_as_timestamp', 10, 3 );
Just in case someone needs that
