It seems that you forgot prints traces on Zend_Date lines 178, 181, 183

 // set datepart
        if (($part !== null && $part !== self::TIMESTAMP) or (!is_numeric($date))) {
print "\n1:".$this->getIso();
            // switch off dst handling for value setting
            $this->setUnixTimestamp($this->getGmtOffset());
print "\n2:".$this->getIso();
            $this->set($date, $part, $this->_locale);
print "\n3:".$this->getIso();

Here the patch for Zend/Date.php

Index: Date.php
===================================================================
--- Date.php    (revision 14118)
+++ Date.php    (working copy)
@@ -175,12 +175,9 @@
 
         // set datepart
         if (($part !== null && $part !== self::TIMESTAMP) or (!is_numeric($date))) {
-print "\n1:".$this->getIso();
             // switch off dst handling for value setting
             $this->setUnixTimestamp($this->getGmtOffset());
-print "\n2:".$this->getIso();
             $this->set($date, $part, $this->_locale);
-print "\n3:".$this->getIso();
 
             // DST fix
             if ((is_array($date) === true) and (isset($date['hour']) === true)) {