Daytime / Night time greeting

Okay I’m going to try and explain this as best as possible. I am curious to know if anybody knows of some type of code or whatever it may be (java for HTML or AS for flash?) that changes to the time on your computer when somebody visits your site? Now to explain this, I have a flash file on my front page that has a picture of a desert scene in daylight and I have another pic with the same desert scene taken at night. What I’m wondering is when people come to my site during the day they’ll see the “daytime” pic and if they come to the site after a certain time in the evening I want them to come to the same “home” page but with the “night time” picture showing instead and it’ll say something like “Good Evening”. I just want whatever pic to display at the appropriate time. I’ve seen this done before on another site and figured since that whole site was done in flash if anybody knew what I can use for code or AS to do that. Not sure if it was java within his HTML page or if it was AS within the flash file but need it to work with other browsers besides IE such as Netscape/Firefox etc.
Does anybody know of something like this? Any help would be very much appreciated. Thanks.