calculating date diff and then adding it to a date

Let's say:
$termdate = 9/10/11
$addeddate = 8/11/11
$nowdate = 9/23/11

The result is calculated at 13 days diff and $newtermdate will be 09/23/11. That is fine.

However let's say:
$termdate = 12/09/11
$addeddate = 8/11/11
$nowdate = 9/23/11

The result is still calculated at 13 days diff and $newtermdate will be 12/22/11. That is obviously wrong. Any ideas?

$termdate = $row['termdate'];
$addeddate = $row['date'];
$nowdate = date("m/d/y");

$diff = abs(strtotime($nowdate) - strtotime($addeddate));

$years = floor($diff / (365*60*60*24));
$months = floor(($diff - $years * 365*60*60*24) / (30*60*60*24));
$days = floor(($diff - $years * 365*60*60*24 - $months*30*60*60*24)/ (60*60*24));

$newtermdate = strtotime('+'.$days.' day', strtotime($termdate));
$newtermdate = date('m/d/y', $newtermdate);

PHP:

 

Try setting your dates as strings instead of pulling them from the database. See if it works as expected. If so, there may be a problem with the data you are pulling from the database.

$termdate = '2011-09-10';
$addeddate = '2011-08-11';
$nowdate = date("m/d/y");

$diff = abs(strtotime($nowdate) - strtotime($addeddate));

$years = floor($diff / (365*60*60*24));
$months = floor(($diff - $years * 365*60*60*24) / (30*60*60*24));
$days = floor(($diff - $years * 365*60*60*24 - $months*30*60*60*24)/ (60*60*24));

$newtermdate = strtotime('+'.$days.' day', strtotime($termdate));
$newtermdate = date('m/d/y', $newtermdate);
echo $newtermdate;

PHP:

 

Why is 12/22/11 not 13 days later than 12/9/11? 9 + 13 = 22 the last time I looked. Did I miss something? (You're using m/d/y format.)