I haven't tried this for real but you can export the Calendar folder as a 'pst' file and then import it into your home system. I'm not sure whether you'll get the option to merge or overwrite when you do it.
A good way of doing this would be to export your calendar to excel and then save it on a floppy, you can then import it at home. Not entirely sure of how the calendar would work, but I have done this with contacts and had no problems.
Do a backup of your 'pst' file before trying it then you can replace it if it goes wrong. I know that when you import a normal mail folder you get various options to overwrite or merge as I did this at work yesterday.