I need a calendar that stores everything locally as I work from places that don't have internet sometimes (I'm a virtual office). I really can't figure it out from reading what I can find about the subject. I am using Mint 12.
Mozilla Thunderbird plus lightning addon (official replacement for Sunbird which is no longer actively maintained)
There is plenty of calendar software for Linux. Depending of your needs and desktop environment that you use you can choose from:
I strongly recommend you to use Mozilla Sunbird.