If you use the php Datetime class you could use:
function time_ago(Datetime $date) {
$time_ago = '';
$diff = $date->diff(new Datetime('now'));
if (($t = $diff->format("%m")) > 0)
$time_ago = $t . ' months';
else if (($t = $diff->format("%d")) > 0)
$time_ago = $t . ' days';
else if (($t = $diff->format("%H")) > 0)
$time_ago = $t . ' hours';
else
$time_ago = 'minutes';
return $time_ago . ' ago (' . $date->format('M j, Y') . ')';
}