Many of Google Calendar's advanced functions rely on the fact that it's a Web service. With most other calendar software, you'd either access the program from your own computer's hard drive or you'd store the application on a local area network (LAN). With Google Calendar, the entire application and all its contents are on the Web.
One of the Web services Google takes advantage of is short message service (SMS) support. This is the format cell phones use to send text messages. Users can allow Google Calendar to send reminders via SMS to their cell phones. As a scheduled event draws near, Google Calendar sends an alert via SMS to a phone number registered by the respective user. While Google offers this as a free service, users may have to pay their cell phone service providers if they go over their monthly text message limits.
Google fosters a growing community of developers who use Google's application programming interface (API) to build new programs based off Google technology. Google calls the resulting applications Google gadgets. Many developers design gadgets to work with existing applications, including Google Calendar. Gadgets allow users to insert special events into a calendar. The options are practically limitless. Examples can include everything from inserting a relevant photograph to attaching a Google Map showing the location of the event.
Google Calendar makes it pretty easy to send invitations to other people. First, you create an event in your own calendar and fill out the details. Then, you can click on the "add guests" option. This opens up a field in which you can type e-mail addresses. Once you save the event, Google Calendar sends e-mails to the invite list. As guests respond to the invite, Google Calendar displays the results within the event listing on your calendar.
If a user chooses to share or publish a calendar, other users can leave comments on event entries. This allows people to discuss upcoming appointments or debrief after a meeting. The event page becomes a forum for guests and calendar viewers.
What does Google use to keep the Google Calendar system up and running? Find out in the next section.