Update CHANGELOG.md

Author: llaske

CHANGELOG.md

@@ -4,7 +4,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
-## [1.4.0] - 2020-03-23
+## [1.4.0] - 2020-09-23
 ### Added
 - Fraction activity #205
 - Implode activity #710