Common subdirectories: date/date and date-New/date
diff -up date/date_api.module date-New/date_api.module
--- date/date_api.module	2009-08-13 12:57:27.000000000 +0200
+++ date-New/date_api.module	2010-01-10 21:17:36.000000000 +0100
@@ -1039,6 +1039,18 @@ function date_difference($date1_in, $dat
  * chosen first day of week for this site.
  */
 function date_week_range($week, $year) {
+  if (variable_get('date_api_are_weeknumbers_iso8601', FALSE)) {
+    $last_week_of_year = date("W",strtotime(($year-1)."-"."12-31"));
+    $last_day_of_year  = date("w",strtotime(($year-1)."-"."12-31"));
+    if ($last_day_of_year > 3) {
+      if ($week == $last_week_of_year) {
+        $week=1;
+      }
+      else {
+	$week++;
+      }
+    }
+  }
   $min_date = date_make_date($year .'-01-01 00:00:00', date_default_timezone_name());
   date_timezone_set($min_date, date_default_timezone());
 
@@ -1093,15 +1105,19 @@ function date_week($date) {
   $year_week = intval(date_format($year_date, 'W'));
   $date_year = intval(date_format($date, 'o'));
 
-  // remove the leap week if it's present
-  if ($date_year > intval($parts[0])) {
-    $last_date = drupal_clone($date);
-    date_modify($last_date, '-7 days');
-    $week = date_format($last_date, 'W') + 1;
-  } else if ($date_year < intval($parts[0])) {
-    $week = 0;
+  // Underlying database functions produce ISO-8601 week numbers.
+  // If we aren't using ISO-8601 week numbers, adjust.
+  if (!variable_get('date_api_are_weeknumbers_iso8601', FALSE)) {
+    // remove the leap week if it's present
+    if ($date_year > intval($parts[0])) {
+      $last_date = drupal_clone($date);
+      date_modify($last_date, '-7 days');
+      $week = date_format($last_date, 'W') + 1;
+    } else if ($date_year < intval($parts[0])) {
+      $week = 0;
+    }
+    if ($year_week != 1) $week++;
   }
-  if ($year_week != 1) $week++;
 
   // convert to ISO-8601 day number, to match weeks calculated above
   $iso_first_day = 1 + (variable_get('date_first_day', 0) + 6) % 7;
@@ -2391,6 +2407,8 @@ function date_api_system_modules_submit(
  * This form section is now part of the form at 'admin/settings/date-time/formats'.
  * We add the formats as values to the form to avoid errors on submission
  * of the form when expected values are missing in system_date_time_settings_submit().
+ *
+ * Add a form element to configure whether or not week numbers are ISO-8601 (default: FALSE == US/UK/AUS norm).
  */
 function date_api_form_system_date_time_settings_alter(&$form, $form_state, $form_id = 'system_date_time_settings') {
   include_once(drupal_get_path('module', 'date_api') .'/date_api.admin.inc');
@@ -2404,6 +2422,12 @@ function date_api_form_system_date_time_
       unset($form['date_formats'][$key]);
     }
   }
+  $form['locale']['date_api_are_weeknumbers_iso8601'] = array(
+    '#type'          => 'checkbox',
+    '#title'         => t('Use ISO-8601 week numbers.  Important! First Day of week MUST be set to Monday if this option is checked.'),
+    '#default_value' => variable_get('date_api_are_weeknumbers_iso8601', FALSE),
+  );
+  $form = system_settings_form($form);
 }
 
 /**
Common subdirectories: date/date_locale and date-New/date_locale
Common subdirectories: date/date_php4 and date-New/date_php4
Common subdirectories: date/date_popup and date-New/date_popup
Common subdirectories: date/date_repeat and date-New/date_repeat
Common subdirectories: date/date_timezone and date-New/date_timezone
Common subdirectories: date/date_tools and date-New/date_tools
Common subdirectories: date/help and date-New/help
Common subdirectories: date/images and date-New/images
Common subdirectories: date/includes and date-New/includes
Common subdirectories: date/tests and date-New/tests
Common subdirectories: date/theme and date-New/theme
Common subdirectories: date/translations and date-New/translations