Convert int to time

Hi,

I am having a problem converting integers to time. I am getting the right data but when I am trying to convert it I get an error or a different date.

Here’s my code:
case ‘_date_printed’ :
$platform = get_post_meta( $post_id, ‘_date_printed’, true );
//$output = strtotime($platform);
if( empty($platform)) $platform = ”;
echo ‘<span>’.$platform.'</span>’; // display the data
break;

And this is the output:

And when I try to convert it to time:

case ‘_date_printed’ :
$platform = get_post_meta( $post_id, ‘_date_printed’, true );
$output = strtotime($platform);
if( empty($output )) $output = ”;
echo ‘<span>’.$output .'</span>’; // display the data
break;

Here’s the output: