Update changelog for new release

CHANGELOG.md

@@ -5,8 +5,17 @@ All changes important to the user will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/)
 
+## [Unreleased]
+### Added
+
+### Changed
+
+### Removed
+
+### Fixed
+
 
-## [4.0.0] - Unreleased (PyPWA-Next)
+## [4.0.0] - 2022-9-10
 ### Added
 - Anaconda environments. There are two anaconda environments included
   inside the source folder at the moment. `anaconda-environment.yml` and
@@ -296,7 +305,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/)
 - Packaging
 
 [Unreleased]: https://github.com/JeffersonLab/PyPWA/compare/v3.3.0...main
-[3.3.0]: https://github.com/JeffersonLab/PyPWA/compare/v3.2.2...v.3.2.3
+[4.0.0]: https://github.com/JeffersonLab/PyPWA/compare/v3.4.0...v.4.0.0
+[3.4.0]: https://github.com/JeffersonLab/PyPWA/compare/v3.3.0...v.3.4.0
+[3.3.0]: https://github.com/JeffersonLab/PyPWA/compare/v3.2.3...v.3.3.0
 [3.2.3]: https://github.com/JeffersonLab/PyPWA/compare/v3.2.2...v.3.2.3
 [3.2.2]: https://github.com/JeffersonLab/PyPWA/compare/v3.2.1...3.2.2
 [3.2.1]: https://github.com/JeffersonLab/PyPWA/compare/v3.2.0...v3.2.1