Jun 28th, 2010
To add Yahoo! Calendar is quite easy, just follow below steps:
1. Right click the calendar select Manage Calendar…
2. Click “New…” button.
3. Select “CalDav Calendar” and click Next
4. Select “CalDav Calendar on Yahoo!” and click Next
5. Input your Yahoo! account info and the calendar name, click Finish to add the calendar.
To sync your iPhone calendar with Desktop iCalendar via Yahoo! is also very easy.
If you have the new iPhone 3.0 Firmware and have switched to the new Yahoo Calender via http://switch.calendar.yahoo.com you can add the calendar via Settings -> Mail, Contacts, Calendars -> Add Account -> Other ->Add CalDAV Account. Use caldav.calendar.yahoo.com as the server.(From Yahoo! Answers)
Yahoo! Calendar supports syncing To-do list, which is better than Google Calendar. I do not know why Google keeps Task API as a secret. There is a feature request on Google forum which has been 1 year now. More than hundred people asked Google to release Task API, but nobody responds it.