diff --git a/lib/Kolab/FreeBusy/Utils.php b/lib/Kolab/FreeBusy/Utils.php
--- a/lib/Kolab/FreeBusy/Utils.php
+++ b/lib/Kolab/FreeBusy/Utils.php
@@ -178,7 +178,7 @@
 	{
 		// use date from HTTP query
 		if (!empty($_GET['dtstart'])) {
-			return self::periodStartDT()->format('u');
+			return self::periodStartDT()->format('U');
 		}
 
 		// Should probably be a setting. For now, do 8 weeks in the past
@@ -194,8 +194,14 @@
 	{
 		// use date from HTTP query
 		if (!empty($_GET['dtstart']) &&
-				($dtstart = \rcube_utils::anytodatetime(filter_input(INPUT_GET, 'dtstart', FILTER_SANITIZE_STRING)))) {
-			return $dtstart;
+				($dtstart = filter_input(INPUT_GET, 'dtstart', FILTER_SANITIZE_STRING))
+		) {
+			try {
+				return new \DateTime($dtstart, new \DateTimezone('UTC'));
+			}
+			catch (Exception $e) {
+				// ignore
+			}
 		}
 
 		// Should probably be a setting. For now, do 8 weeks in the past
@@ -211,7 +217,7 @@
 	{
 		// use date from HTTP query
 		if (!empty($_GET['dtend'])) {
-			return self::periodEndDT()->format('u');
+			return self::periodEndDT()->format('U');
 		}
 
 		// Should probably be a setting. For now, do 16 weeks into the future
@@ -227,8 +233,14 @@
 	{
 		// use date from HTTP query
 		if (!empty($_GET['dtend']) &&
-				($dtend = \rcube_utils::anytodatetime(filter_input(INPUT_GET, 'dtend', FILTER_SANITIZE_STRING)))) {
-			return $dtend;
+			($dtend = filter_input(INPUT_GET, 'dtend', FILTER_SANITIZE_STRING))
+		) {
+			try {
+				return new \DateTime($dtend, new \DateTimezone('UTC'));
+			}
+			catch (Exception $e) {
+				// ignore
+			}
 		}
 
 		// Should probably be a setting. For now, do 8 weeks in the past
@@ -259,4 +271,4 @@
 
 		return $dummy;
 	}
-}
\ No newline at end of file
+}
diff --git a/public_html/index.php b/public_html/index.php
--- a/public_html/index.php
+++ b/public_html/index.php
@@ -74,6 +74,8 @@
 	#header('Content-type: text/calendar; charset=utf-8', true);
 	header('Content-type: text/plain; charset=utf-8', true);
 
+	list($uri, $args) = explode('?', $uri);
+
 	// analyse request
 	$url = array_filter(explode('/', $uri));
 	$user = strtolower(array_pop($url));