This plugin allows to show or hide content at specific times.
The original author, K. Though, stopped the development by the end of 2016. In March 2017 I have taken over the development since I use it in one website myself.
You can find the source at GitHub.
You find the exact description how to use it on the plugin page at WordPress.
Compared to the version as of March 2017 the current version has been revised fundamentally. Date values are now always in ISO format (yyyy-mm-dd), eventhough older shortcodes and rules should mostly still work. Many problems have been fixed and the code was refactored according to the PHP standards recommendation (PSR).