I maintain a website for a car club I belong to. I have been looking for two years - trying to find a calendar program that suits our needs. Zap Calendar has fit the bill and I am happy with it. The most amazing part of my experience with Zap is the support offered. I encountered a problem with an add-on which displays 12 months at the top of the calendar and reported it to Dan. He communicated well and worked tirelessly on the issue until a solution was found.
Ah yes - this is what service is. Now I remember. If you are looking for a good extension to replace a finicky component such as JEvents - this is the one to go with.
Highly recommended for it's features as well as support.