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Bug #19383 Date->converttz($tz) fails for timezones in western hemisphere
Submitted: 2002-09-12 20:04 UTC Modified: 2002-09-12 22:12 UTC
From: asutton at sbcglobal dot net Assigned:
Status: Not a bug Package: Date/time related
PHP Version: 4.2.3 OS: Linux
Private report: No CVE-ID: None
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From: asutton at sbcglobal dot net
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 [2002-09-12 20:04 UTC] asutton at sbcglobal dot net 
When using Date.php, the converttz($tz) function does not properly convert the date if the timezone offset from gmt
is negative. The problem appears to be caused by a typo in the converttz function which causes subtractSeconds() to be
called with a negative value. In a nutshell, the abs() should be applied to the subtractSeconds() argument, not the addSeconds(). I have included a patch which has completely eliminated the problem, as far as I can test. One could also make a case for ammending subtractSeconds() and addSeconds() to catch negative values.

Here's a script which demonstrates the problem:

---Cut Here---
<html>
<body>
<?php

require_once("Date.php");
require_once("Date/TimeZone.php");

$mydate = new Date("2002-05-06 20:21:22");
$mylocaltz = new Date_Timezone("US/Central");

print "UTC: " . $mydate->format("%Y-%m-%d %H:%M:%S") . "<br>\n";

$mydate->converttz($mylocaltz);

print "CDT: " . $mydate->format("%Y-%m-%d %H:%M:%S") . "<br>\n";

?>
</body>
</html>
---Cut Here---

The output on my system is:

UTC: 2002-05-06 20:21:22
CDT: 2002-05-06 25:21:22

Note that it is going the wrong way, and that the hours is greater than 23! This isn't even a valid date.

Here's the patch:

---Cut Here---
*** ../Date.php Fri Jun 21 20:58:20 2002
--- Date.php    Thu Sep 12 17:16:42 2002
***************
*** 440,452 ****
          } else {
              $this->addSeconds(intval(abs($this->tz->getOffset($this)) / 1000))
;
          }
          // convert UTC to new timezone
          if($tz->getOffset($this) > 0) {
!             $this->addSeconds(intval(abs($tz->getOffset($this)) / 1000));
          } else {
!             $this->subtractSeconds(intval($tz->getOffset($this) / 1000));
          }
          $this->tz = $tz;
      }

      /**
--- 440,452 ----
          } else {
              $this->addSeconds(intval(abs($this->tz->getOffset($this)) / 1000))
;
          }
          // convert UTC to new timezone
          if($tz->getOffset($this) > 0) {
!             $this->addSeconds(intval($tz->getOffset($this) / 1000));
          } else {
!             $this->subtractSeconds(intval(abs($tz->getOffset($this)) / 1000));
          }
          $this->tz = $tz;
      }

      /**
---Cut Here---

Thanks,

Allan

--
Allan Sutton
asutton@sbcglobal.net

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 [2002-09-12 20:16 UTC] asutton at sbcglobal dot net 
Nevermind. It looks like this has already been fixed in version 1.6 of Date.php, so it'll be ok in the next release.

Thanks,

Allan
 [2002-09-12 22:12 UTC] sniper@php.net 
okay..
 
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