In order to share the contents of calendar(s) you need to sync the contents.
If you own multiple iOS devices, simply plug them into the same computer and sync the calendars from iTunes:http://support.apple.com/kb/HT1296
You can also use a sharing service like iCloud to keep all your devices in sync so there is no need to plug them in: http://www.apple.com/icloud/setup/
If you are trying to share your calendar with someone else (you don't have physicial access to their iPhone) then you can use iCloud to share your calendar with them: http://support.apple.com/kb/PH2690
Well it would.....but this is the dealeo...... I have my iphone 4s and my fiance just got the 3gs. We are trying to figure out if she shoud just have her own profile on the mac, own itunes, and own icloud and i just share the calendar with her or share my itune account so she can access my library. She has no music.....her computer is long gone and her library with it.....
I would appreciate any hints tips r thoughts