Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.925
diff -u -r1.925 common.inc
--- includes/common.inc	18 Jun 2009 21:19:01 -0000	1.925
+++ includes/common.inc	25 Jun 2009 14:25:54 -0000
@@ -1909,38 +1909,43 @@
       $format = variable_get('date_format_medium', 'D, m/d/Y - H:i');
   }
 
-  $max = strlen($format);
-  $date = '';
   // Create a DateTime object from the timestamp.
   $date_time = date_create('@' . $timestamp);
   // Set the time zone for the DateTime object.
   date_timezone_set($date_time, $timezones[$timezone]);
 
-  for ($i = 0; $i < $max; $i++) {
-    $c = $format[$i];
-    if (strpos('AaeDlMT', $c) !== FALSE) {
-      $date .= t(date_format($date_time, $c), array(), array('langcode' => $langcode));
-    }
-    elseif ($c == 'F') {
-      // Special treatment for long month names: May is both an abbreviation
-      // and a full month name in English, but other languages have
-      // different abbreviations.
-      $date .= t(date_format($date_time, $c), array(), array('context' => 'Long month name', 'langcode' => $langcode));
-    }
-    elseif (strpos('BcdGgHhIijLmNnOoPSstUuWwYyZz', $c) !== FALSE) {
-      $date .= date_format($date_time, $c);
-    }
-    elseif ($c == 'r') {
-      $date .= format_date($timestamp, 'custom', 'D, d M Y H:i:s O', $timezone, $langcode);
-    }
-    elseif ($c == '\\') {
-      $date .= $format[++$i];
-    }
-    else {
-      $date .= $c;
+  // Replace characters in format string which need to be translated, 'X', with
+  // an arbitrary escape sequence '+=X=+'. The 'F' format character, long month
+  // name, requires special handling (see below). These patterns exclude any
+  // format characters which have been escaped with '\' (octal 134).
+  $format = preg_replace(array('@(?<!\134)r@', '@(?<!\134)([FAaeDlMTBcdGgHhIijLmNnOoPSstUuWwYyZz])@'), array('D, d M Y H:i:s O', '+=$1=+'), $format);
+
+  $replace_from = array();
+  $replace_to = array();
+
+  // Now look for any escape sequences and translate them.
+  if (preg_match_all('@\+=([FAaeDlMTBcdGgHhIijLmNnOoPSstUuWwYyZz])=\+@', $format, $matches)) {
+    $matches[1] = array_unique($matches[1]);
+
+    // Make a single call to date_format() using the format string.
+    $replacements = explode('|', date_format($date_time, implode('|', $matches[1])));
+
+    foreach ($matches[1] as $index => $match) {
+      $replace_from[] = "+=$match=+";
+      if ($match == 'F') {
+        // Special treatment for long month names: May is both an abbreviation
+        // and a full month name in English, but other languages have
+        // different abbreviations.
+        $replace_to[] = t($replacements[$index], array(), array('context' => 'Long month name', 'langcode' => $langcode));
+      }
+      else {
+        $replace_to[] = t($replacements[$index], array(), array('langcode' => $langcode));
+      }
     }
   }
 
+  $date = str_replace($replace_from, $replace_to, $format);
+
   return $date;
 }