Any suggestions on calendar software that a teacher could use to keep a timetable in?

Basically, we have a 2 week rotating timetable. We've tried Outlook and this works fine, but as soon as we hit half term the weeks went out of sync. What we could do with is a program that lets you add an exception to a recurring event so that you can skip the half term week.

Has anyone got any advice on how to do this?