For the most part these days, sharing calendars can be very easy with the likes of Google Calendar and iCal/iCloud. Of course, when people you share with use other calendar apps it can be difficult.

If you use your Mac in a home environment, or want to allow your kids to use your Mac without the scare of them messing with your own data and account, there are a few steps to ensure safe and appropriate use by everyone. And the nice part is that it's all built-in to your beautiful Mac OS. No third-party software required.