There are many different plugins available that allows you to hide or edit WordPress Howdy message which shows up on the top right corner or admin bar and is visible only to logged in users. This tutorial explains you how you can change that Howdy message and add some greetings depending on the time of the day. For Example: If its morning time the plugin will display Good Morning message as shown in the given screenshot.
Installation & Usage: Simply install and activate the plugin Greet Admin by Time and you are done. It automatically starts working after activation, there are no configuration settings to make.