diff --git a/php/PublicHolidayCalendar.php b/php/PublicHolidayCalendar.php
index 431c280..e853f1a 100644
--- a/php/PublicHolidayCalendar.php
+++ b/php/PublicHolidayCalendar.php
@@ -30,23 +30,32 @@ class PublicHolidayCalendar {
      * - YearStart: int The start year of the calendar (with century). Default : current year
      * - YearNumber: int The number of year fo the calendar. Default : 5
      * - WeeksNumbers: bool (0/1) Include weeks number ? Default : 0
+     * - debug: bool(0/1)
      *
      * All times are UTC
      *
      * @return void
      */
     #[NoReturn] public function proceed (): void {
+        $debug = !isset($_GET['debug']) || $_GET['debug'] == '' ? 0 : $_GET['debug'];
+        if (preg_match('#^\s*(?<bool>[01])?\s*$#i', $debug, $match) !== 1) {
+            $debug = false;
+        }
+        else {
+            $debug = isset($match['bool']) && $match['bool'];
+        }
+
         try {
             //region Extract arguments
             //region YearStart
-            $yearStart = $_GET['YearStart'] == '' ? (new DateTimeImmutable('now'))->format('Y') : $_GET['YearStart'];
+            $yearStart = !isset($_GET['YearStart']) || $_GET['YearStart'] == '' ? (new DateTimeImmutable('now'))->format('Y') : $_GET['YearStart'];
             if (!is_numeric($yearStart)) {
                 throw new UnexpectedValueException('The "YearStart" argument must be an integer');
             }
             $yearStart = intval($yearStart);
             //endregion
             //region YearNumber
-            $yearNumber = $_GET['YearNumber'] == '' ? 5 : $_GET['YearNumber'];
+            $yearNumber = !isset($_GET['YearNumber']) || $_GET['YearNumber'] == '' ? 5 : $_GET['YearNumber'];
             if (!is_numeric($yearNumber)) {
                 throw new UnexpectedValueException('The "YearNumber" argument must be a strictly positive integer');
             }
@@ -56,17 +65,17 @@ class PublicHolidayCalendar {
             }
             //endregion
             //region WeeksNumbers
-            $weeksNumbers = $_GET['WeeksNumbers'] == '' ? 0 : $_GET['WeeksNumbers'];
+            $weeksNumbers = !isset($_GET['WeeksNumbers']) || $_GET['WeeksNumbers'] == '' ? 0 : $_GET['WeeksNumbers'];
             if (preg_match('#^\s*(?<bool>[01])?\s*$#i', $weeksNumbers, $match) !== 1) {
                 throw new UnexpectedValueException('The "WeeksNumber" argument must be a boolean (0 or 1)');
             }
-            $weeksNumbers = isset($match['bool']) && $match['false'];
+            $weeksNumbers = isset($match['bool']) && $match['bool'];
             //endregion
             //endregion
 
             //region Create the calendar
             $calendar = new Calendar();
-            $calendar->addTimeZone(TimeZone::createFromPhpDateTimeZone(new DateTimeZone(DateTimeZone::UTC)));
+            $calendar->addTimeZone(TimeZone::createFromPhpDateTimeZone(new DateTimeZone('UTC')));
 
             $yearEnd = $yearStart + $yearNumber;
             for ($yearCurrent = $yearStart; $yearCurrent <= $yearEnd; $yearCurrent++) {
@@ -81,16 +90,25 @@ class PublicHolidayCalendar {
             $icalFactory = new CalendarFactory();
             $icalContent = (string)$icalFactory->createCalendar($calendar);
 
-            header('Content-Type: text/calendar; charset=UTF-8', true, 200);
-            header('Content-Length: ' . mb_strlen($icalContent));
-            header('Content-Disposition: attachment; filename=PublicHolidayCalendar.ics');
+            if ($debug) {
+                header('Content-Type: text/plain; charset=UTF-8', true, 200);
+            }
+            else {
+                header('Content-Type: text/calendar; charset=UTF-8', true, 200);
+                header('Content-Length: ' . strlen($icalContent));          // Don't use mb_strlen because we NEED the number of bytes
+                header('Content-Disposition: attachment; filename=PublicHolidayCalendar.ics');
+            }
             echo $icalContent;
             exit(0);
             //endregion
         }
         catch (Throwable $e) {
             header('Content-Type: text/plain; charset=UTF-8', true, 500);
-            echo $e->getMessage();
+            echo 'Exception [' . get_class($e) . ']: ' . $e->getMessage() . PHP_EOL;
+            if ($debug) {
+                echo $e->getTraceAsString() . PHP_EOL;
+            }
+
             exit(1);
         }
     }
@@ -182,7 +200,7 @@ class PublicHolidayCalendar {
         $currentDayOfWeek = (int)$currentDay->format('N');
         if ($currentDayOfWeek > 1) {
             try {
-                $currentDay = $currentDay->sub(new DateInterval('P' . (8 - $currentDayOfWeek) . 'D'));
+                $currentDay = $currentDay->add(new DateInterval('P' . (8 - $currentDayOfWeek) . 'D'));
             }
             catch (Exception) {
             }
@@ -192,7 +210,7 @@ class PublicHolidayCalendar {
         while ($currentDay < $lastDay) {
             $events[] = static::createEvent(
                 'Semaine ' . (count($events) + 1),
-                'Semaine n° ' . (count($events) + 1),
+                'Semaine ' . (count($events) + 1),
                 false,
                 $currentDay
             );
@@ -313,7 +331,7 @@ class PublicHolidayCalendar {
     private static function createEvent (string $summary, string $description, bool $publicHoliday, DateTimeInterface $date): Event {
         return (new Event(new UniqueIdentifier(hash('sha256', $date->format('Y-m-d')))))
             ->setSummary($summary)
-            ->setDescription($description . ($publicHoliday ? ' - Férié' : ''))
+            ->setDescription($description . ' ' . $date->format('Y') . ($publicHoliday ? ' - Férié' : ''))
             ->setOccurrence(new SingleDay(new Date($date)));
     }