This is un-tested code, but it’s how I use it:
<?php
$event = $post->AirpressCollection[0];
$sDate = new DateTime($event["Start"]);
$eDate = new DateTime($event["End"]);
echo $sDate->format("Y-m-d H:i:s");
echo $eDate->format("Y-m-d H:i:s");
?>
Is that what you’re asking? If not, show me what you currently do and I’ll try again.
More date formatting options here:
https://php.net/manual/en/function.date.php