Yahoo's online calendar is free and easy to use, but lacks some of the features of Google's alternative.
You can share your calendars with other people fairly easily, but it's less obvious at a glance how to get other people's calendars to show up on your page. You're limited to one calendar, although you can categorise the events on it with a finite number of descriptions (appointment, call, lunch, or meeting, for instance); however, you can only sort by this information in the Event List view. Other calendars, including both your friends' and those for any Yahoo Groups you belong to, are displayed as what Yahoo terms Time Guides.
They can either be intermingled with your own events or displayed in separate columns. There are other public calendars available, but they are limited to sports team schedules, financial events, and holidays. While you can set up your calendar to be visible to anybody with a web browser, if you want to restrict access to certain people, they will need to have a Yahoo account as well.
Yahoo Calendar lets you send yourself reminders of upcoming events by scheduling notifications. You can elect to receive these reminders via email, a text message to your mobile phone, or your Yahoo Messenger account. In order to get reminders to an email address other than your Yahoo account, you'll have to add that address to your account profile and verify it.
Unfortunately, while you can set up reminders for two separate times, you can't specify different types of notifications for different times - for instance, you couldn't send yourself a reminder email two hours before an event, and an SMS half an hour before the same event. Instead, Yahoo Calendar will send both the email and the SMS at both of the times you choose.
If you want to use your Yahoo Calendar in conjunction with other calendaring programs, you can export and import data - but only to or from Palm Desktop and Outlook. Yahoo has a synching client called Autosync, but it's compatible only with Windows. If you want to synchronise with iCal, you'll have to go through a multistep workaround. And, as is true with other online calendars, you'll lose access to your Yahoo Calendar when you don't have an internet connection.
For those looking to keep track of a simple personal schedule, Yahoo Calendar might serve: it's free and it offers basic calendaring and task functions. But if you have more complex needs, you'll want to look elsewhere - perhaps to iCal or Google Calendar.