If you have a date time stamp and want to check it against another date time to check if its older than a certain amount of days here is how to do it with PHP:

$date = date("Y-m-d h:i");//2017-09-23 11:21
if (strtotime($date) < strtotime('-2 days')) {
   echo 'Date is older than 2 days';
 } else {
   echo 'Date is not older than 2 days';
}

if (strtotime($date) < strtotime('-14 days')) {
   echo 'Date is older than 14 days';
 } else { 
echo 'Date is not older than 14 days'; 
}

The code above checks the date time stamp using strtotime and uses and if statement in ordering what is does. Code like this is useful when doing coding a cache check to see if new data needs to be written or if you can fetch old data if it’s still recent.