Processing form input as a date

Hello,

I am using the following code to take 15 minutes from the current date/time

$minus = -900; 

$nowtimeanddate = date("Y-m-d H:i:s");
$nowtimeanddate15 = time($nowtimeanddate) + ($minus);
$nowtimeanddate15 = date("Y-m-d H:i:s", $nowtimeanddate15);

Code (markup):

This works fine but I am trying to use the same thing to process a date submitted by a user but instead of getting changes made to the user's date, I get the time/date now plus/minus whatever variation I feed in.

Anyone see what I'm doing wrong? Here's what I've got:

$thisdate = $_POST['nojsyear']."-".$_POST['nojsmonth']."-".$_POST['nojsday'];
$thistime = $_POST['stt_hour'].":".$_POST['stt_minute'].":".$_POST['stt_seconds'];

$alltimedate = $thisdate." ".$thistime;
$alltimedate = strtotime($alltimedate);
$alltimedate = date("Y-m-d H:i:s", $alltimedate);
$alltimedateUpdated = time($alltimedate) + ($minus);
$alltimedateUpdated = date("Y-m-d H:i:s", $alltimedateUpdated);

Code (markup):

Any help will be greatly appreciated.

 

why

$alltimedateUpdated = date("Y-m-d H:i:s", $tweettimedateUpdated);

Code (markup):

shouldnt it be

$alltimedateUpdated = date("Y-m-d H:i:s", $alltimedateUpdated );

Code (markup):

 

Yeah, you're right. But that was a mistake in explaining the problem, in my actual code I have $alltimedateUpdated

edit: for the purpose of clarity, I have corrected my original post

 

$minus = -900; 

$nowtimeanddate = date("Y-m-d H:i:s");
$nowtimeanddate15 = date("Y-m-d H:i:s", time() + $minus);

Code (markup):

 

That is for the time and date now minus 15 minutes. I want to use a date stored in a variable rather thasn the time and date right now minus 15 mins. Make sense?

 

Well, you can subtract 900 from any number you like.

If your time is stored as a unix timestamp (integer) just subtract 900 from it.

If it's stored in Y-m-d H:i:s, then strtotime it first.

Maybe I am missing something which is making this more complicated than it seems to me.