Rotating Header and Images based on day and time

I am wanting to rotate the header image and images on the main page, together, and side bars to correspond to different events in a day.

Like if we had a two day carnival and there where five main events a day that i could put on a calendar inside the site..

Then at those times and based on the day it would show images based on the event. once the event was over if no other event was show it would got to a default image set.

Example: if event one went from 10am – noon… then the images would display for that even but if the next even didn’t start until 2:30.. then it would show a default image set for the site, then at 2:30-3:30 would show a set for the next event.

Hope that makes sense.
How can i do this?
Thank you!