Anytime greeting is ready for your website user. Time Based Greeting
This plugin can be used for Greeting your website users with different messages and images depending on Time of the Day.
As an administrator of the website you can adjust Time Settings for Morning,Afternoon,Evening and Night in (0-23) hour clock format.(1 means 1 AM and 13 means 1 PM).With these time settings You can write messages that you wish to display during that time.You can also give link of the images that you wish to display during that time duration.This plugin is widgetized so you can drag it to the side bar and you can display it in whichever position you want on your website.For managing all this a very simple and clean interface is given.
I am sure you will find it very easy and useful.