6 reasons to use Google Calendar (besides it being FREE!):
Let your co-workers, family, and friends see your calendar, and view schedules that others have shared with you. When you know when everyone is free or busy, scheduling is a snap.
With two-way syncing to your mobile phone's built-in calendar or a mobile version of Google Calendar that's made for the small screen, you can access your calendar while you're away from your desk.
Customizable reminders help you stay on schedule. You can choose to be notified by email or get a text message sent right to your mobile phone.
Invite other people to events on your calendar. Guests can RSVP to your events by email or via Google Calendar.
Know where you're supposed to be even when you don't have internet access. With offline access, you can view a read-only version of your calendar no matter where you are.