diff --git a/src/Freq.php b/src/Freq.php
index 7f78abe..2454cb4 100644
--- a/src/Freq.php
+++ b/src/Freq.php
@@ -404,7 +404,7 @@ private function validDate($t) {
 	 * @param int $offset
 	 * @return int
 	 */
-	public function findEndOfPeriod($offset) {
+	public function findEndOfPeriod($offset = 0) {
 		return $this->findStartingPoint($offset, 1, false);
 	}