[plt-scheme] Question about calendar in scheme (plt)

It has been bugging me for a while, so I was wondering if anyone knows
of a calendar program in scheme?

One thing that I have not been able to find easily, is a calendar
program that allows you to have the information sitting somewhere on the
net, and connect from where you happen to be, ie. I use a mac, linux and
netbsd box all removed networkwise and geographically.

Anyone have any ideas?  I have had a reality check recently on my
programming abilities (and time available) so could anyone give me an
idea on how difficult this might be? and ways to go about starting? 
Projects that might already have implemented parts of what I want to do?

Am downloading schemeunit to get ready.;-)

Thanks all, 

Rohan