[Zope] Calendar tag released

People have been asking for my Calendar tag product, so I've uploaded a beta version to the contributed software page. With the DateTime class fixed in zope 1.10.x, it should be stable (in 1.9, misccalculations sometimes cause botches like repeated days). Have fun, and let me know what you think. When I get a chance I'll probably add a Year mode and polish up the documentation and call it 1.0.