PHP从格式创建而不是正确格式化时间

I have this time string from sql 00:05:00 and I need a timestamp from it but can't seem to get it. I have also tried strtotime.

What am I doing wrong?

$NonBillable = '00:05:00';
$NonBillable = DateTime::createFromFormat('H:i:s', $NonBillable)->getTimestamp();
echo $NonBillable;

$NonBillable = DateTime::createFromFormat('H:i:s', '00:05:00');
echo $NonBillable->getTimestamp();

It results for me 1464480300 -> Sun, 29 May 2016 00:05:00 GMT because no date has been given, it uses today.

So a simple solution to this would be:

echo $NonBillable->getTimestamp() - time();