• Change version constants in src/Constants.php
• Adjust the file UPGRADING.md with version specific information
• Adjust the versions in SECURITY.md
• Push a release branch called release-x.x and merge it as last PR into master
• Publish the release

Post release task:

• Website: Change version in _config.yml and key kimai_v2_version
• Website: Create a new version announcement post, including the release notes
• Twitter: share a link to the new release