instead of get_field('time_picker_name', $post_id)
try get_field('time_picker_name', $post_id, false)
The third argument tells ACF not to format the value. To be honest, I’ve never used a date field in ACF as much as I’ve used ACF. But not formatting the value should work I think.
$formatted_date = '';
if (get_field('date_completed', $post_id, false) {
$date = get_field('date_completed', $post_id);
$date_completed = new DateTime($date);
$formatted_date = $date_completed->format('M j Y');
}