The first thing that comes to my mind when I hear "WordPress" and "calendar" is the default calendar widget, with a WordPress post by date. But WordPress calendar plugins covers a much larger - and more powerful - array of plugins. This is a wordpress event calendar plugin
https://www.psd2html.com/blog/the-top-w ... -paid.html for events, orders and appointments. Some turn WordPress into their own work application, while others offer the right set of tools to create a fully functional timesheet and payment gateway.