Few days after releasing Google Calendar, Google Calendar API have just been released in beta stage to provide fonctionnalities for read/write within your calendar. Currently you can Request the calendar’s feeds, Add an event and Send a date-range query. As an API I find it complicated and not very professional, maybe this is related to the nature of the application itself and to keep the implementation more easy to use with feeds like API.
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Google Calendar allows client applications to view and update calendar events in the form of Google data API (“GData”) feeds. Your client application can use the Google Calendar data API to create new events, edit or delete existing events, and query for events that match particular criteria.
There are many possible uses for the Calendar data API. For example, you can create a web front end for your group’s calendar that uses Google Calendar as a back end. Or you can generate a public calendar for Google Calendar to display, based on your organization’s event database. Or you can search relevant calendars to display a list of upcoming events on those calendars.