How can arraign preset image rotation, or..

[Umm... Idk...]

Hi, I'm new so I hope this is the correct area. I want to do something like this:
http://www.codingforums.com/archive/...hp/t-7115.html

I want to put an image of the zodiac signs on my site and to set it to change monthly without me having to do it by hand, I don't just mean monthly, I want to set it to change according to the approximate dates of the signs and remain there until the next scheduled sign date, that would be fine

but my real "vision" is more complex: A composite image that changes with the time of day, monthly, yearly, with varied transparencies, auto-cropping and to retrieve data from ephemeris files - but I don't know how to do any of this and will really need help, so please drop me a line if you think you can assist me!

Thanks for any help you guys can contribute!