The text on the main page with the convention date and location is now clickable:
Clicking on the link downloads a little file of calendar information, and allows you to add Potlatch 23 to your calendar. Check it out.
It took me a while to figure out how to do this. I thought it would involve microformats, which are way cool, but in this case they are not the answer. Just create an event in your calendar app, export it, upload the .ics file to the site, and add a link. Old school, simple, and works with the latest smartphones.