This plugin allows you to display timed content.
You have 3 time windows to display your content. Originally, this plugin was made to display a notice before a event starts, a 2nd notice during the event and a 3rd after the event has been closed. you can define the time when each of these 3 time wondows should be display individually, also the content can be set independently for each of the 3 time windows.
Timewindows plugin - display 3 different time wondows with different content. You could eg display a countdown for a upcoming event, a message during the event and a thank you message after the event.