Here is the simple solution
1) Tap on "
Settings" from your main screen on iPhone.
2) Tap on "*Mail, Contacts, Calendars*"
3) Tap on "*Add Account...*"
4) Tap on "
Other" (At the bottom)
5) Tap on "*Add CalDav Account*" (Second from the bottom)
6) If you are using Google calendars, just type in the word "
google" (without the quotes) for the server
7) User Name is your gmail address (Example: username@gmail.com)
8) Password is your gmail password
9) Description can be whatever you want it to be.
10) Tap the "
Next" button on the upper right.
11) Start using your Calendar!
* For
Yahoo Calendars, follow the exact same steps above, but instead of typing "google" for the server, type "
yahoo" (Without the quotes) and your user name will be your Yahoo email address. (Example: username@yahoo.com)
Also, for Yahoo - Make sure you have upgraded your Yahoo calendar to the latest beta version. You can mae sure you are using the Beta calendar by clicking the following link:
http://switch.calendar.yahoo.com
I hope this helps!
It works perfectly for both calendar systems. My wife and I now have a shared calendar which we can both edit from our iPhones and iCal. Cool stuff!