Oh common...
It's a playlist management software with some receiving software on the other end.
Playlist management:
iTunes
Streaming:
http://www.rogueamoeba.com/nicecast/
Receiving:
iTunes (or any other media player that is capable of receiving Icecast streams [most players can now])
Edit:
Hrm... I missed your "time of day" and remote management...
A cron task with an Applescript could easily deal with different playlists throughout the day... Not exactly sure how easy it would be to remotely manage the playlists though. Any ideas? What I'm thinking of right now would be allowing people to remotely log into the server, and have folder actions on tracks that correspond to the playlist. like a folder named "afternoon" which will automatically add any mp3s or wmas added to it to a playlist called "afternoon" which due to a cron task, will start playing at noon. Or it could be way more specialized, who knows.
Another thing is, you could use iHam on iRye to remotely change songs or shuffle or something.