Index: wp-mail.php
===================================================================
--- wp-mail.php	(revision 17572)
+++ wp-mail.php	(working copy)
@@ -147,7 +147,14 @@
 					}
 				}
 
-				$time_zn = intval($date_arr[4]) * 36;
+				// of the form "-0430"
+				$offset = $date_arr[4];
+				$time_zn_H = intval( substr( $offset, 0, strlen($offset) - 2 ) );	// "-04" -> -4 hours
+				$time_zn_i = intval( substr( $offset, strlen($offset) - 2 ) );		// "30" -> 30 minutes
+				$time_zn_i *= $time_zn_H / abs( $time_zn_H );											// -30 minutes = 30 * -1 = 30 * (-4 / 4) = 30 * (-4 / abs(-4))
+				$time_zn = $time_zn_H * 60 + $time_zn_i;													// -270 mintues = -240 + -30 = (-4 * 60) + -30
+				$time_zn *= 60;																										// -16200 seconds = -270 * 60
+
 				$ddate_U = gmmktime($ddate_H, $ddate_i, $ddate_s, $ddate_m, $ddate_d, $ddate_Y);
 				$ddate_U = $ddate_U - $time_zn;
 				$post_date = gmdate('Y-m-d H:i:s', $ddate_U + $time_difference);