18 digit timestamp?

Question

I am working on a system related to tv recordings.

I am parsing the following xml from another system (to which i have no documentation):

Answer 1

$dateLargeInt= "131424999530821857";
$secsAfterADEpoch = $dateLargeInt / (10000000); 
$ADToUnixConvertor=((1970-1601) * 365.242190) * 86400;
// unix epoch - AD epoch * number of tropical days * seconds in a day 
$unixTsLastLogon=intval($secsAfterADEpoch-$ADToUnixConvertor); 

// unix Timestamp version of AD timestamp
$lastlogon=date("d-m-Y", $unixTsLastLogon); // formatted date

echo $lastlogon;